task.py

import abc
import ast
import logging
import random
import re
from collections.abc import Callable
from copy import deepcopy
from dataclasses import asdict, dataclass
from inspect import getsource
from typing import (
    Any,
    Dict,
    Iterable,
    Iterator,
    List,
    Literal,
    Mapping,
    Optional,
    Tuple,
    Union,
)

import datasets
import numpy as np
from tqdm import tqdm

from lm_eval import utils
from lm_eval.api import samplers
from lm_eval.api.instance import Instance, OutputType
from lm_eval.api.metrics import bits_per_byte, mean, weighted_perplexity
from lm_eval.api.registry import (
    AGGREGATION_REGISTRY,
    DEFAULT_METRIC_REGISTRY,
    get_aggregation,
    get_metric,
    get_metric_aggregation,
    is_higher_better,
)
from lm_eval.caching.cache import load_from_cache, save_to_cache
from lm_eval.filters import build_filter_ensemble
from lm_eval.prompts import get_prompt


ALL_OUTPUT_TYPES = [
    "loglikelihood",
    "multiple_choice",
    "loglikelihood_rolling",
    "generate_until",
]

eval_logger = logging.getLogger("lm-eval")


@dataclass
class TaskConfig(dict):
    # task naming/registry
    task: Optional[str] = None
    task_alias: Optional[str] = None
    group: Optional[Union[str, list]] = None
    group_alias: Optional[Union[str, list]] = None
    # HF dataset options.
    # which dataset to use,
    # and what splits for what purpose
    dataset_path: Optional[str] = None
    dataset_name: Optional[str] = None
    dataset_kwargs: Optional[dict] = None
    training_split: Optional[str] = None
    validation_split: Optional[str] = None
    test_split: Optional[str] = None
    fewshot_split: Optional[
        str
    ] = None  # TODO: assert that this not None if num_fewshot > 0. (?) assert if this is same split as one evaling (?)
    # formatting / prompting options.
    # see docs/advanced_task_guide.md for more info
    process_docs: Optional[Callable] = None
    doc_to_text: Optional[Union[Callable, str]] = None
    doc_to_target: Optional[Union[Callable, str]] = None
    doc_to_choice: Optional[Union[Callable, str, dict, list]] = None
    process_results: Optional[Union[Callable, str]] = None
    use_prompt: Optional[str] = None
    description: str = ""
    target_delimiter: str = " "
    fewshot_delimiter: str = "\n\n"
    fewshot_config: Optional[dict] = None
    # runtime configuration options
    num_fewshot: Optional[int] = None
    # scoring options
    metric_list: Optional[list] = None
    output_type: OutputType = "generate_until"
    generation_kwargs: Optional[dict] = None
    repeats: int = 1
    filter_list: Optional[Union[str, list]] = None
    should_decontaminate: bool = False
    doc_to_decontamination_query: Optional[str] = None
    metadata: Optional[
        dict
    ] = None  # by default, not used in the code. allows for users to pass arbitrary info to tasks

    def __post_init__(self) -> None:
        if self.generation_kwargs is not None:
            if self.output_type != "generate_until":
                eval_logger.warning(
                    f"[{self.task}] passed `generation_kwargs`, but not using `output_type: generate_until`!"
                )

            if "temperature" in self.generation_kwargs:
                self.generation_kwargs["temperature"] = float(
                    self.generation_kwargs["temperature"]
                )

            if "until" not in self.generation_kwargs:
                self.generation_kwargs["until"] = [self.fewshot_delimiter]
        else:
            if self.output_type == "generate_until":
                # ensure that we greedily generate in absence of explicit arguments otherwise
                self.generation_kwargs = {
                    "until": (
                        None
                        if self.fewshot_delimiter is None
                        else [self.fewshot_delimiter]
                    ),
                    "do_sample": False,
                }

    def __getitem__(self, item):
        return getattr(self, item)

    def __setitem__(self, item, value):
        return setattr(self, item, value)

    def to_dict(self, keep_callable: bool = False) -> dict:
        """dumps the current config as a dictionary object, as a printable format.
        null fields will not be printed.
        Used for dumping results alongside full task configuration

        :return: dict
            A printable dictionary version of the TaskConfig object.

        # TODO: should any default value in the TaskConfig not be printed?
        """
        cfg_dict = asdict(self)
        # remove values that are `None`
        for k, v in list(cfg_dict.items()):
            if v is None:
                cfg_dict.pop(k)
            elif k == "metric_list":
                for metric_dict in v:
                    for metric_key, metric_value in metric_dict.items():
                        if callable(metric_value):
                            metric_dict[metric_key] = self.serialize_function(
                                metric_value, keep_callable=keep_callable
                            )
                cfg_dict[k] = v
            elif callable(v):
                cfg_dict[k] = self.serialize_function(v, keep_callable=keep_callable)
        return cfg_dict

    def serialize_function(
        self, value: Union[Callable, str], keep_callable=False
    ) -> Union[Callable, str]:
        """Serializes a given function or string.

        If 'keep_callable' is True, the original callable is returned.
        Otherwise, attempts to return the source code of the callable using 'getsource'.
        """
        if keep_callable:
            return value
        else:
            try:
                return getsource(value)
            except (TypeError, OSError):
                return str(value)


class Task(abc.ABC):
    """A task represents an entire benchmark including its dataset, problems,
    answers, and evaluation methods. See BoolQ for a simple example implementation

    A `doc` can be any python object which represents one instance of evaluation.
    This is usually a dictionary e.g.
        {"question": ..., "answer": ...} or
        {"question": ..., question, answer)
    """

    VERSION: Optional[Union[int, str]] = None

    # The name of the `Task` benchmark as denoted in the HuggingFace datasets Hub
    # or a path to a custom `datasets` loading script.
    DATASET_PATH: Optional[str] = None

    # The name of a subset within `DATASET_PATH`.
    DATASET_NAME: Optional[str] = None

    OUTPUT_TYPE: Optional[OutputType] = None

    def __init__(
        self,
        data_dir: Optional[str] = None,
        cache_dir: Optional[str] = None,
        download_mode: Optional[datasets.DownloadMode] = None,
        config: Optional[Mapping] = None,  # Union[dict, TaskConfig]
    ) -> None:
        """
        :param data_dir: str
            Stores the path to a local folder containing the `Task`'s data files.
            Use this to specify the path to manually downloaded data (usually when
            the dataset is not publicly accessible).
        :param cache_dir: str
            The directory to read/write the `Task` dataset. This follows the
            HuggingFace `datasets` API with the default cache directory located at:
                `~/.cache/huggingface/datasets`
            NOTE: You can change the cache location globally for a given process
            to another directory:
                `export HF_DATASETS_CACHE="/path/to/another/directory"`
        :param download_mode: datasets.DownloadMode
            How to treat pre-existing `Task` downloads and data.
            - `datasets.DownloadMode.REUSE_DATASET_IF_EXISTS`
                Reuse download and reuse dataset.
            - `datasets.DownloadMode.REUSE_CACHE_IF_EXISTS`
                Reuse download with fresh dataset.
            - `datasets.DownloadMode.FORCE_REDOWNLOAD`
                Fresh download and fresh dataset.
        """
        self.download(data_dir, cache_dir, download_mode)
        self._training_docs: Optional[list] = None
        self._fewshot_docs: Optional[list] = None
        self._instances: Optional[List[Instance]] = None

        self._config: TaskConfig = TaskConfig({**config}) if config else TaskConfig()

        self._filters = [build_filter_ensemble("none", [["take_first", None]])]
        self.fewshot_rnd: Optional[
            random.Random
        ] = None  # purposely induce errors in case of improper usage

    def download(
        self,
        data_dir: Optional[str] = None,
        cache_dir: Optional[str] = None,
        download_mode=None,
    ) -> None:
        """Downloads and returns the task dataset.
        Override this method to download the dataset from a custom API.

        :param data_dir: str
            Stores the path to a local folder containing the `Task`'s data files.
            Use this to specify the path to manually downloaded data (usually when
            the dataset is not publicly accessible).
        :param cache_dir: str
            The directory to read/write the `Task` dataset. This follows the
            HuggingFace `datasets` API with the default cache directory located at:
                `~/.cache/huggingface/datasets`
            NOTE: You can change the cache location globally for a given process
            by setting the shell environment variable, `HF_DATASETS_CACHE`,
            to another directory:
                `export HF_DATASETS_CACHE="/path/to/another/directory"`
        :param download_mode: datasets.DownloadMode
            How to treat pre-existing `Task` downloads and data.
            - `datasets.DownloadMode.REUSE_DATASET_IF_EXISTS`
                Reuse download and reuse dataset.
            - `datasets.DownloadMode.REUSE_CACHE_IF_EXISTS`
                Reuse download with fresh dataset.
            - `datasets.DownloadMode.FORCE_REDOWNLOAD`
                Fresh download and fresh dataset.
        """
        self.dataset = datasets.load_dataset(
            path=self.DATASET_PATH,
            name=self.DATASET_NAME,
            data_dir=data_dir,
            cache_dir=cache_dir,
            download_mode=download_mode,
        )

    @property
    def config(self) -> TaskConfig:
        """Returns the TaskConfig associated with this class."""
        return self._config

    @abc.abstractmethod
    def has_training_docs(self):
        """Whether the task has a training set"""
        pass

    @abc.abstractmethod
    def has_validation_docs(self):
        """Whether the task has a validation set"""
        pass

    @abc.abstractmethod
    def has_test_docs(self):
        """Whether the task has a test set"""
        pass

    def training_docs(self) -> Iterable:
        """
        :return: Iterable[obj]
            A iterable of any object, that doc_to_text can handle
        """
        return []

    def validation_docs(self) -> Iterable:
        """
        :return: Iterable[obj]
            A iterable of any object, that doc_to_text can handle
        """
        return []

    def test_docs(self) -> Iterable:
        """
        :return: Iterable[obj]
            A iterable of any object, that doc_to_text can handle
        """
        return []

    def fewshot_docs(self) -> Iterable:
        """
        :return: Iterable[obj]
            A iterable of any object, that doc_to_text can handle
        """
        if self.has_training_docs():
            return self.training_docs()
        elif self.has_validation_docs():
            return self.validation_docs()
        else:
            eval_logger.warning(
                f"[Task: {self.config.task}] has_training_docs and has_validation_docs are False"
                ", using test_docs as fewshot_docs but this is not recommended."
            )
            return self.test_docs()

    def _process_doc(self, doc: dict) -> dict:
        """
        Override this to process (detokenize, strip, replace, etc.) individual
        documents. This can be used in a map over documents of a data split.
        E.g. `map(self._process_doc, self.dataset["validation"])`

        :return: dict
            The processed version of the specified `doc`.
        """
        return doc

    @property
    def instances(self) -> List[Instance]:
        """After calling `task.build_all_requests()`, tasks
        maintain a list of the dataset instances which will be evaluated.
        """
        return self._instances

    def fewshot_examples(self, k, rnd):
        if self._training_docs is None:
            self._training_docs = list(self.training_docs())

        return rnd.sample(self._training_docs, k)

    def doc_to_decontamination_query(self, doc):
        raise NotImplementedError(
            "Override doc_to_decontamination_query with document specific decontamination query."
        )

    @abc.abstractmethod
    def doc_to_text(self, doc):
        pass

    @abc.abstractmethod
    def doc_to_target(self, doc):
        pass

    def build_all_requests(
        self,
        *,
        limit=None,
        rank=None,
        world_size=None,
        cache_requests=False,
        rewrite_requests_cache=False,
        system_instruction=None,
        apply_chat_template=False,
        fewshot_as_multiturn=False,
        tokenizer=None,
    ) -> None:
        """Build a set of Instances for a task, and store them in task.instances"""

        # used with caching
        og_limit = limit

        cache_key = f"requests-{self._config.task}-{self.config.num_fewshot}shot-rank{rank}-world_size{world_size}"

        cached_instances = load_from_cache(file_name=cache_key)

        if cache_requests and cached_instances and not rewrite_requests_cache:
            cached_instances = cached_instances[:limit]

            flattened_instances = [
                instance
                for instance_group in cached_instances
                for instance in instance_group
            ]

            self._instances = flattened_instances
            return

        eval_logger.info(f"Building contexts for {self.config.task} on rank {rank}...")

        instances = []

        # process all documents when caching is specified for simplicity
        if (
            cache_requests
            and (not cached_instances or rewrite_requests_cache)
            and limit is not None
        ):
            limit = None

        doc_id_docs = list(
            self.doc_iterator(rank=rank, limit=limit, world_size=world_size)
        )

        num_docs = len(doc_id_docs)

        for doc_id, doc in tqdm(
            doc_id_docs,
            total=num_docs,
        ):
            # sample fewshot context #TODO: need to offset doc_id by rank now!
            fewshot_ctx = self.fewshot_context(
                doc,
                0 if self.config.num_fewshot is None else self.config.num_fewshot,
                system_instruction,
                apply_chat_template,
                fewshot_as_multiturn,
                tokenizer,
            )

            # TODO: we should override self.config.repeats if doing greedy gen so users don't waste time+compute
            inst = self.construct_requests(
                doc=doc,
                ctx=fewshot_ctx,
                metadata=(self.config["task"], doc_id, self.config.repeats),
            )

            if not isinstance(inst, list):
                inst = [inst]

            instances.append(inst)

        # now flatten, this is to allow slicing to work with pickles

        sliced_instances = instances[:og_limit]

        flattened_instances = [
            instance
            for instance_group in sliced_instances
            for instance in instance_group
        ]

        self._instances = flattened_instances

        if len(self._instances) == 0:
            raise ValueError("task.build_requests() did not find any docs!")

        if cache_requests and (not cached_instances or rewrite_requests_cache):
            save_to_cache(file_name=cache_key, obj=instances)

    @abc.abstractmethod
    def construct_requests(self, doc, ctx, **kwargs):
        """Uses RequestFactory to construct Requests and returns an iterable of
        Requests which will be sent to the LM.

        :param doc:
            The document as returned from training_docs, validation_docs, or test_docs.
        :param ctx: str
            The context string, generated by fewshot_context. This includes the natural
            language description, as well as the few shot examples, and the question
            part of the document for `doc`.
        :param doc_idx: int
            The index of a document within `self.test_docs()` or `self.validation_docs()`,
            whichever is the main split used.
        :param repeats: int
        TODO: update this docstring
            The number of times each instance in a dataset is inferred on. Defaults to 1,
            can be increased for techniques like majority voting.
        """
        pass

    @abc.abstractmethod
    def process_results(self, doc, results):
        """Take a single document and the LM results and evaluates, returning a
        dict where keys are the names of submetrics and values are the values of
        the metric for that one document

        :param doc:
            The document as returned from training_docs, validation_docs, or test_docs.
        :param results:
            The results of the requests created in construct_requests.
        """
        pass

    @abc.abstractmethod
    def aggregation(self):
        """
        :returns: {str: [metric_score] -> float}
            A dictionary where keys are the names of submetrics and values are
            functions that aggregate a list of metric scores
        """
        pass

    @abc.abstractmethod
    def higher_is_better(self):
        """
        :returns: {str: bool}
            A dictionary where keys are the names of submetrics and values are
            whether a higher value of the submetric is better
        """
        pass

    def get_config(self, key: str) -> Any:
        return getattr(self._config, key, None)

    @classmethod
    def count_bytes(cls, doc):
        """Used for byte-level perplexity metrics in rolling loglikelihood"""
        return len(doc.encode("utf-8"))

    @classmethod
    def count_words(cls, doc):
        """Downstream loglikelihood_rolling perplexity tasks with custom word boundaries should override this!"""
        return len(re.split(r"\s+", doc))

    @utils.positional_deprecated
    def fewshot_context(
        self,
        doc,
        num_fewshot,
        rnd=None,
        description=None,
    ):
        """Returns a fewshot context string that is made up of a prepended description
        (if provided), the `num_fewshot` number of examples, and an appended prompt example.

        :param doc: str
            The document as returned from training_docs, validation_docs, or test_docs.
        :param num_fewshot: int
            The number of fewshot examples to provide in the returned context string.
        :param rnd: random.Random
            The pseudo-random number generator used to randomly sample examples.
            WARNING: This is currently a required arg although it's optionalized with a default `None`.
        :param description: str
            The task's description that will be prepended to the fewshot examples.
        :returns: str
            The fewshot context.
        """
        if rnd is None:
            if self.fewshot_rnd is not None:
                rnd = self.fewshot_rnd
            else:
                raise ValueError(
                    "A `random.Random` generator argument must be provided to `rnd`"
                )

        description = description if description else ""

        if num_fewshot == 0:
            labeled_examples = ""
        else:
            # for sets with no training docs, draw from other set *but ensure no overlap with current doc*
            if self.has_training_docs():
                fewshotex = self.fewshot_examples(k=num_fewshot, rnd=rnd)
            else:
                if self._fewshot_docs is None:
                    self._fewshot_docs = list(
                        self.validation_docs()
                        if self.has_validation_docs()
                        else self.test_docs()
                    )

                fewshotex = rnd.sample(self._fewshot_docs, num_fewshot + 1)

                # get rid of the doc that's the one we're evaluating, if it's in the fewshot
                fewshotex = [x for x in fewshotex if x != doc][:num_fewshot]

            labeled_examples = (
                "\n\n".join(
                    [
                        self.doc_to_text(doc) + self.doc_to_target(doc)
                        for doc in fewshotex
                    ]
                )
                + "\n\n"
            )

        example = self.doc_to_text(doc)
        return description + labeled_examples + example

    def apply_filters(self) -> Optional[List[Instance]]:
        """Iterates over FilterEnsembles and applies them to instances"""
        if hasattr(self, "_filters"):
            for f in self._filters:
                f.apply(self._instances)
        else:
            eval_logger.warning("No filter defined, passing through instances")
            return self._instances

    def dump_config(self) -> dict:
        """Returns the config as a dictionary."""
        # TODO: this should only return the overrides applied to a non-YAML task's configuration.
        # (num_fewshot)
        return self.config.to_dict()

    def set_config(self, key: str, value: Any, update: bool = False) -> None:
        """Set or update the configuration for a given key."""
        if key is None:
            raise ValueError("Key must be provided.")

        if update:
            current_value = getattr(self._config, key, {})
            if not isinstance(current_value, dict):
                raise TypeError(
                    f"Expected a dict for key '{key}', got {type(current_value).__name__} instead."
                )
            current_value.update(value)
        else:
            setattr(self._config, key, value)

    def override_metric(self, metric_name: str) -> None:
        """
        Override the default metrics used for evaluation with custom metrics.

        Parameters:
        - metric_name (str): The name of the custom metric to override. Should be registered in api.metrics.
        """
        (
            self._metric_fn_list,
            self._aggregation_list,
            self._metric_fn_kwargs,
            self._higher_is_better,
        ) = ({}, {}, {}, {})
        self._metric_fn_list[metric_name] = get_metric(metric_name)
        self._aggregation_list[metric_name] = get_metric_aggregation(metric_name)
        self._higher_is_better[metric_name] = is_higher_better(metric_name)
        self._metric_fn_kwargs[metric_name] = {}
        if not isinstance(self, ConfigurableTask):
            self.process_results = lambda x, y: {metric_name: get_metric(metric_name)}
            self.aggregation = lambda: {
                metric_name: get_metric_aggregation(metric_name)
            }
        setattr(self._config, "metric_list", [{"metric": metric_name}])
        setattr(self._config, "process_results", None)

    def set_fewshot_seed(self, seed: Optional[int] = None) -> None:
        self.fewshot_rnd = random.Random(seed)
        if hasattr(self, "sampler"):
            self.sampler.rnd = self.fewshot_rnd

    @property
    def eval_docs(self) -> Union[datasets.Dataset, List[dict]]:
        if self.has_test_docs():
            return self.test_docs()
        elif self.has_validation_docs():
            return self.validation_docs()
        else:
            raise ValueError(
                f"Task dataset (path={self.DATASET_PATH}, name={self.DATASET_NAME}) must have valid or test docs!"
            )

    def doc_iterator(
        self, *, rank: int = 0, limit: Union[int, None] = None, world_size: int = 1
    ) -> Iterator[Tuple[int, Any]]:
        limit = int(limit) if limit else None
        doc_iterator = utils.create_iterator(
            enumerate(self.eval_docs),
            rank=int(rank),
            limit=limit,
            world_size=int(world_size),
        )
        return doc_iterator


class ConfigurableTask(Task):
    VERSION = "Yaml"
    OUTPUT_TYPE = None
    CONFIG = None

    def __init__(
        self,
        data_dir=None,
        cache_dir=None,
        download_mode=None,
        config: Optional[dict] = None,
    ) -> None:  # TODO no super() call here
        # Get pre-configured attributes
        self._config = self.CONFIG

        # Use new configurations if there was no preconfiguration
        if self.config is None:
            self._config = TaskConfig(**config)
        # Overwrite configs
        else:
            if config is not None:
                self._config.__dict__.update(config)

        if self.config is None:
            raise ValueError(
                "Must pass a config to ConfigurableTask, either in cls.CONFIG or `config` kwarg"
            )

        if isinstance(self.config.metadata, dict):
            if "version" in self.config.metadata:
                self.VERSION = self.config.metadata["version"]

        if self.config.output_type is not None:
            if self.config.output_type not in ALL_OUTPUT_TYPES:
                raise ValueError(
                    f"Got invalid output_type '{self.config.output_type}', must be in '{','.join(ALL_OUTPUT_TYPES)}'"
                )
            self.OUTPUT_TYPE = self.config.output_type

        if self.config.dataset_path is not None:
            self.DATASET_PATH = self.config.dataset_path

        if self.config.dataset_name is not None:
            self.DATASET_NAME = self.config.dataset_name

        self._metric_fn_list = {}
        self._metric_fn_kwargs = {}
        self._aggregation_list = {}
        self._higher_is_better = {}

        if self.config.metric_list is None:
            # TODO: handle this in TaskConfig.__post_init__ ?
            _metric_list = DEFAULT_METRIC_REGISTRY[self.config.output_type]

            for metric_name in _metric_list:
                self._metric_fn_list[metric_name] = get_metric(metric_name)
                self._metric_fn_kwargs[metric_name] = {}
                self._aggregation_list[metric_name] = get_metric_aggregation(
                    metric_name
                )
                self._higher_is_better[metric_name] = is_higher_better(metric_name)
        else:
            for metric_config in self.config.metric_list:
                if "metric" not in metric_config:
                    raise ValueError(
                        "'metric' key not provided for an entry in 'metric_list', must be specified!"
                    )
                metric_name = metric_config["metric"]
                kwargs = {
                    key: metric_config[key]
                    for key in metric_config
                    if key
                    not in ["metric", "aggregation", "higher_is_better", "hf_evaluate"]
                }
                hf_evaluate_metric = (
                    "hf_evaluate" in metric_config
                    and metric_config["hf_evaluate"] is True
                )

                if self.config.process_results is not None:
                    self._metric_fn_list[metric_name] = None
                    self._metric_fn_kwargs[metric_name] = {}
                elif callable(metric_name):
                    metric_fn = metric_name.__call__
                    metric_name = metric_name.__name__
                    self._metric_fn_list[metric_name] = metric_fn
                    self._metric_fn_kwargs[metric_name] = kwargs
                else:
                    self._metric_fn_list[metric_name] = get_metric(
                        metric_name, hf_evaluate_metric
                    )
                    self._metric_fn_kwargs[metric_name] = kwargs

                if "aggregation" in metric_config:
                    agg_name = metric_config["aggregation"]
                    if isinstance(agg_name, str):
                        self._aggregation_list[metric_name] = get_aggregation(agg_name)
                    elif callable(agg_name):  # noqa: E721
                        self._aggregation_list[metric_name] = metric_config[
                            "aggregation"
                        ]
                else:
                    INV_AGG_REGISTRY = {v: k for k, v in AGGREGATION_REGISTRY.items()}
                    metric_agg = get_metric_aggregation(metric_name)
                    eval_logger.warning(
                        f"[Task: {self.config.task}] metric {metric_name} is defined, but aggregation is not. "
                        f"using default "
                        f"aggregation={INV_AGG_REGISTRY[metric_agg]}"
                    )
                    self._aggregation_list[metric_name] = metric_agg

                if "higher_is_better" in metric_config:
                    self._higher_is_better[metric_name] = metric_config[
                        "higher_is_better"
                    ]
                else:
                    eval_logger.warning(
                        f"[Task: {self.config.task}] metric {metric_name} is defined, but higher_is_better is not. "
                        f"using default "
                        f"higher_is_better={is_higher_better(metric_name)}"
                    )
                    self._higher_is_better[metric_name] = is_higher_better(metric_name)

        self.download(self.config.dataset_kwargs)
        self._training_docs = None
        self._fewshot_docs = None

        if self.config.filter_list is not None:
            self._filters = []
            for filter_config in self.config.filter_list:
                filter_name = filter_config["name"]
                filter_functions = filter_config["filter"]
                components = []
                for function in filter_functions:
                    kwargs = {
                        key: function[key] for key in function if key != "function"
                    }
                    components.append([function["function"], kwargs])
                filter_pipeline = build_filter_ensemble(filter_name, components)
                self._filters.append(filter_pipeline)
        else:
            self._filters = [build_filter_ensemble("none", [["take_first", None]])]

        if self.config.use_prompt is not None:
            eval_logger.info(f"loading prompt {self.config.use_prompt}")
            self.prompt = get_prompt(
                self.config.use_prompt, self.DATASET_PATH, self.DATASET_NAME
            )
        else:
            self.prompt = None

        if self.fewshot_docs() is not None:
            self.fewshot_rnd = (
                random.Random()
            )  # setting with no seed, to be overridden at a later time
            config_sampler: Union[str, Callable] = (
                self.config.fewshot_config.get("sampler", "default")
                if self.config.fewshot_config
                else "default"
            )
            if isinstance(config_sampler, str):
                self.sampler = samplers.get_sampler(config_sampler)(
                    list(self.fewshot_docs()), self, rnd=self.fewshot_rnd
                )
            elif callable(config_sampler) and issubclass(
                config_sampler, samplers.ContextSampler
            ):
                self.sampler = config_sampler(
                    docs=list(self.fewshot_docs()), task=self, rnd=self.fewshot_rnd
                )
            else:
                raise TypeError(
                    f"fewshot_config.sampler should be a string or callable of ContextSampler type, "
                    f"not {type(config_sampler)}"
                )

        self.task_docs = self.eval_docs

        # Test One Doc
        self.features = list(self.task_docs.features.keys())
        self.multiple_input = 0
        self.multiple_target = 0
        test_doc = self.task_docs[0]
        test_text = self.doc_to_text(test_doc)
        test_target = self.doc_to_target(test_doc)

        if self.config.doc_to_choice is not None:
            test_choice = self.doc_to_choice(test_doc)
            if not isinstance(test_choice, list):
                eval_logger.error("doc_to_choice must return list")
            else:
                num_choice = len(test_choice)

            if isinstance(test_text, int):
                self.multiple_input = num_choice
        else:
            test_choice = None

        if isinstance(test_target, list):
            self.multiple_target = len(test_target)
        else:
            if (isinstance(test_target, int)) and (test_choice is not None):
                test_target = test_choice[test_target]
            else:
                test_target = str(test_target)

        if test_choice is not None:
            check_choices = test_choice
        else:
            check_choices = [test_target]
        if self.config.doc_to_choice is not None:
            for choice in check_choices:
                choice_has_whitespace = True if choice[0].isspace() else False
                delimiter_has_whitespace = (
                    True
                    if self.config.target_delimiter.rstrip()
                    != self.config.target_delimiter
                    else False
                )

                if delimiter_has_whitespace and choice_has_whitespace:
                    eval_logger.debug(
                        f'Both target_delimiter "{self.config.target_delimiter}" and target choice: "{choice}" have whitespace'
                    )
                elif (not delimiter_has_whitespace) and (not choice_has_whitespace):
                    eval_logger.debug(
                        f'Both target_delimiter "{self.config.target_delimiter}" and target choice: "{choice}" do not have whitespace, ignore if the language you are evaluating on does not require/use whitespace'
                    )

    def download(self, dataset_kwargs: Optional[Dict[str, Any]] = None) -> None:
        self.dataset = datasets.load_dataset(
            path=self.DATASET_PATH,
            name=self.DATASET_NAME,
            **dataset_kwargs if dataset_kwargs is not None else {},
        )

    def has_training_docs(self) -> bool:
        if self.config.training_split is not None:
            return True
        else:
            return False

    def has_validation_docs(self) -> bool:
        if self.config.validation_split is not None:
            return True
        else:
            return False

    def has_test_docs(self) -> bool:
        if self.config.test_split is not None:
            return True
        else:
            return False

    def training_docs(self) -> datasets.Dataset:
        if self.has_training_docs():
            if self.config.process_docs is not None:
                return self.config.process_docs(
                    self.dataset[self.config.training_split]
                )
            return self.dataset[self.config.training_split]

    def validation_docs(self) -> datasets.Dataset:
        if self.has_validation_docs():
            if self.config.process_docs is not None:
                return self.config.process_docs(
                    self.dataset[self.config.validation_split]
                )
            return self.dataset[self.config.validation_split]

    def test_docs(self) -> datasets.Dataset:
        if self.has_test_docs():
            if self.config.process_docs is not None:
                return self.config.process_docs(self.dataset[self.config.test_split])
            return self.dataset[self.config.test_split]

    def fewshot_docs(self):
        if self.config.fewshot_split is not None:
            if self.config.process_docs is not None:
                return self.config.process_docs(self.dataset[self.config.fewshot_split])
            return self.dataset[self.config.fewshot_split]
        else:
            if (self.config.num_fewshot is not None) and (self.config.num_fewshot > 0):
                eval_logger.warning(
                    f"Task '{self.config.task}': "
                    "num_fewshot > 0 but fewshot_split is None. "
                    "using preconfigured rule."
                )
            return super().fewshot_docs()

    def convert_chat_history_to_string(self, chat_history: list, tokenizer=None) -> str:
        """Returns chat history tokenized or concatenated as a string.

        :param chat_history: list
            The chat history to convert to a string.
        :param tokenizer:
            Optional tokenizer to use for applying the chat template, if None, the sampler's fewshot_delimiter is used.
        """
        if tokenizer:
            return tokenizer.apply_chat_template(
                chat_history, tokenize=False, add_generation_prompt=True
            )
        else:
            return self.sampler.fewshot_delimiter + "".join(
                f"{s['role']}: {s['content']}" + self.sampler.fewshot_delimiter
                for s in chat_history
            )

    @utils.positional_deprecated
    def fewshot_context(
        self,
        doc: str,
        num_fewshot: int,
        system_instruction: Optional[str] = None,
        apply_chat_template: bool = False,
        fewshot_as_multiturn: bool = False,
        tokenizer=None,
    ) -> str:
        """Returns a fewshot context string that is made up of a prepended description
        (if provided), the `num_fewshot` number of examples, and an appended prompt example.

        :param doc: str
            The document as returned from training_docs, validation_docs, or test_docs.
        :param num_fewshot: int
            The number of fewshot examples to provide in the returned context string.
        :param  system_instruction: str
            System instruction to be applied to the prompt.
        :param apply_chat_template: bool
            Whether to apply the chat template to the fewshot context.
        :param fewshot_as_multiturn: bool
            Whether to provide the fewshot examples as a multiturn conversation or a single user turn.
        :param tokenizer:
            The tokenizer to use for applying the chat template.
        :returns: str
            The fewshot context.
        """

        if apply_chat_template:
            labeled_examples = []
        else:
            labeled_examples = ""

        # get task description
        if description := self.config.description:
            description = utils.apply_template(self.config.description, doc)

        # create system prompt based on the provided system instruction and description
        if system_instruction is not None and description:
            system_prompt = (
                f"{system_instruction}{self.sampler.fewshot_delimiter}{description}"
            )
        elif system_instruction is not None:
            system_prompt = system_instruction
        elif description:
            system_prompt = description
        else:
            system_prompt = ""

        # add system prompt if specified
        if system_prompt:
            if apply_chat_template:
                labeled_examples.append({"role": "system", "content": system_prompt})
            else:
                labeled_examples = system_prompt

        # if few-shot - append examples after the system prompt
        if num_fewshot > 0:
            if apply_chat_template:
                labeled_examples = self.sampler.get_chat_context(
                    doc, num_fewshot, fewshot_as_multiturn, labeled_examples
                )
            else:
                labeled_examples += self.sampler.get_context(doc, num_fewshot)

        example = self.doc_to_text(doc)
        if apply_chat_template:
            if not self.multiple_input:
                if isinstance(example, str):
                    labeled_examples.append({"role": "user", "content": example})
                elif isinstance(example, list):
                    labeled_examples_list = []
                    for ex in example:
                        chat = deepcopy(labeled_examples)
                        chat.append({"role": "user", "content": ex})
                        labeled_examples_list.append(
                            self.convert_chat_history_to_string(chat, tokenizer)
                        )
                    return labeled_examples_list
                elif isinstance(example, int):
                    if self.config.doc_to_choice is not None:
                        choices = self.doc_to_choice(doc)
                        labeled_examples.append(
                            {"role": "user", "content": choices[example]}
                        )
                    else:
                        labeled_examples.append(
                            {"role": "user", "content": str(example)}
                        )
            return self.convert_chat_history_to_string(labeled_examples, tokenizer)
        else:
            if self.multiple_input:
                return labeled_examples
            if isinstance(example, str):
                return labeled_examples + example
            elif isinstance(example, list):
                return [labeled_examples + ex for ex in example]
            elif isinstance(example, int):
                if self.config.doc_to_choice is not None:
                    choices = self.doc_to_choice(doc)
                    return labeled_examples + choices[example]
                else:
                    return labeled_examples + str(example)

    def apply_filters(self):
        """Iterates over FilterEnsembles and applies them to instances"""
        if hasattr(self, "_filters"):
            for f in self._filters:
                f.apply(self._instances)
        else:
            eval_logger.warning("No filter defined, passing through instances")
            return self._instances

    def should_decontaminate(self):
        return self.config.should_decontaminate

    def doc_to_decontamination_query(self, doc):
        if self.config.should_decontaminate:
            if self.config.doc_to_decontamination_query is None:
                return self.doc_to_text(doc)
            else:
                doc_to_decontamination_query = self.config.doc_to_decontamination_query
                if doc_to_decontamination_query in self.features:
                    return doc[doc_to_decontamination_query]
                elif callable(doc_to_decontamination_query):
                    return doc_to_decontamination_query(doc)
                else:
                    return ast.literal_eval(
                        utils.apply_template(
                            self.config.doc_to_decontamination_query, doc
                        )
                    )

    def _process_doc(self, doc: dict) -> dict:
        """
        Override this to process (detokenize, strip, replace, etc.) individual
        documents. This can be used in a map over documents of a data split.
        E.g. `map(self._process_doc, self.dataset["validation"])`

        :return: dict
            The processed version of the specified `doc`.
        """
        return doc

    def doc_to_text(self, doc):
        if self.prompt is not None:
            doc_to_text = self.prompt
        else:
            doc_to_text = self.config.doc_to_text

        if isinstance(doc_to_text, int):
            return doc_to_text
        elif isinstance(doc_to_text, str):
            if doc_to_text in self.features:
                # if self.config.doc_to_choice is not None:
                #     return self.doc_to_choice(doc)[doc[doc_to_text]]
                # else:
                return doc[doc_to_text]
            else:
                text_string = utils.apply_template(doc_to_text, doc)
                if text_string.isdigit() and self._config.doc_to_choice is not None:
                    return ast.literal_eval(text_string)
                else:
                    return text_string
        elif callable(doc_to_text):
            return doc_to_text(doc)
        # Used when applying a Promptsource template
        elif hasattr(doc_to_text, "apply"):
            applied_prompt = doc_to_text.apply(doc)
            if len(applied_prompt) == 2:
                return applied_prompt[0]
            else:
                eval_logger.warning("Applied prompt returns empty string")
                return self.config.fewshot_delimiter
        else:
            print(type(doc_to_text))
            raise TypeError

    def doc_to_target(self, doc: Mapping) -> Union[int, str, list]:
        if self.prompt is not None:
            doc_to_target = self.prompt
        else:
            doc_to_target = self.config.doc_to_target

        if isinstance(doc_to_target, int):
            return doc_to_target
        elif isinstance(doc_to_target, str):
            if doc_to_target in self.features:
                # if self.config.doc_to_choice is not None:
                #     return self.doc_to_choice(doc)[doc[doc_to_target]]
                # else:
                return doc[doc_to_target]
            else:
                target_string = utils.apply_template(doc_to_target, doc)
                if target_string.isdigit() and self._config.doc_to_choice is not None:
                    return ast.literal_eval(target_string)
                elif (
                    len(target_string) >= 2
                    and (target_string[0] == "[")
                    and (target_string[-1] == "]")
                ):
                    try:
                        return ast.literal_eval(target_string)
                    except (SyntaxError, ValueError):
                        return target_string
                else:
                    return target_string
        elif isinstance(doc_to_target, list):
            return doc_to_target
        elif callable(doc_to_target):
            return doc_to_target(doc)
        # Used when applying a Promptsource template
        elif hasattr(doc_to_target, "apply"):
            applied_prompt = doc_to_target.apply(doc)
            if len(applied_prompt) == 2:
                return applied_prompt[1]
            else:
                eval_logger.warning("Applied prompt returns empty string")
                return self.config.fewshot_delimiter
        else:
            raise TypeError

    def doc_to_choice(self, doc: Any) -> List[str]:
        if self.prompt is not None:
            doc_to_choice = self.prompt
        elif self.config.doc_to_choice is None:
            eval_logger.error("doc_to_choice was called but not set in config")
        else:
            doc_to_choice = self.config.doc_to_choice

        if isinstance(doc_to_choice, str):
            if doc_to_choice in self.features:
                return doc[doc_to_choice]
            else:
                return ast.literal_eval(utils.apply_template(doc_to_choice, doc))
        elif isinstance(doc_to_choice, list):
            return doc_to_choice
        elif isinstance(doc_to_choice, dict):
            return list(doc_to_choice.values())
        elif callable(doc_to_choice):
            return doc_to_choice(doc)
        elif hasattr(doc_to_choice, "get_answer_choices_list"):
            return doc_to_choice.get_answer_choices_list(doc)
        else:
            raise TypeError

    def construct_requests(
        self, doc: dict, ctx: str, **kwargs
    ) -> Union[List[Instance], Instance]:
        if self.OUTPUT_TYPE == "loglikelihood":
            arguments = (ctx, self.doc_to_target(doc))
        elif self.OUTPUT_TYPE == "loglikelihood_rolling":
            arguments = (self.doc_to_target(doc),)
        elif self.OUTPUT_TYPE == "multiple_choice":
            choices = self.doc_to_choice(doc)
            target_delimiter = self.config.target_delimiter
            if self.multiple_input:
                # If there are multiple inputs, choices are placed in the ctx
                cont = self.doc_to_target(doc)
                arguments = [
                    (ctx + choice, f"{target_delimiter}{cont}") for choice in choices
                ]
            else:
                # Otherwise they are placed in the continuation
                arguments = [(ctx, f"{target_delimiter}{cont}") for cont in choices]

            request_list = [
                Instance(
                    request_type="loglikelihood",
                    doc=doc,
                    arguments=arg,
                    idx=i,
                    **kwargs,
                )
                for i, arg in enumerate(arguments)
            ]
            # TODO: we should raise a warning telling users this will at most ~2x runtime.
            if "acc_mutual_info" in self._metric_fn_list.keys():
                # if we are calculating multiple choice accuracy
                # using mutual information instead of raw loglikelihood as metric, need unconditional lls.

                # here mutual info refers to calculating
                # log(P(choice|ctx) / P(choice)) = log(P(choice|ctx)) - log(P(choice))
                # in other words normalizing by subtracting the unconditional logprob of each choice.
                request_list.extend(
                    [
                        Instance(
                            request_type="loglikelihood",
                            doc=doc,
                            arguments=("", "{}".format(choice)),
                            idx=i,
                            **kwargs,
                        )
                        for i, choice in enumerate(choices)
                    ]
                )
            return request_list

        elif self.OUTPUT_TYPE == "generate_until":
            arguments = (ctx, deepcopy(self.config.generation_kwargs))

        return Instance(
            request_type=self.OUTPUT_TYPE, doc=doc, arguments=arguments, idx=0, **kwargs
        )

    def process_results(self, doc, results):
        if callable(self.config.process_results):
            return self.config.process_results(doc, results)

        result_dict = {}
        use_metric = list(self._metric_fn_list.keys())
        if self.OUTPUT_TYPE == "loglikelihood":
            results = results[0]
            ll, is_greedy = results
            return {
                **({"perplexity": ll} if "perplexity" in use_metric else {}),
                **({"acc": int(is_greedy)} if "acc" in use_metric else {}),
            }
        elif self.OUTPUT_TYPE == "loglikelihood_rolling":
            (loglikelihood,) = results
            _words = self.count_words(self.doc_to_target(doc))
            _bytes = self.count_bytes(self.doc_to_target(doc))
            return {
                **(
                    {"word_perplexity": (loglikelihood, _words)}
                    if "word_perplexity" in use_metric
                    else {}
                ),
                **(
                    {"byte_perplexity": (loglikelihood, _bytes)}
                    if "byte_perplexity" in use_metric
                    else {}
                ),
                **(
                    {"bits_per_byte": (loglikelihood, _bytes)}
                    if "bits_per_byte" in use_metric
                    else {}
                ),
            }
        elif self.OUTPUT_TYPE == "multiple_choice":
            lls, is_greedy = zip(*results)

            # retrieve choices in List[str] form, to compute choice lengths, etc.
            choices = self.doc_to_choice(doc)
            completion_len = np.array([float(len(i)) for i in choices])

            if (
                2 * len(choices) == len(lls)
                and "acc_mutual_info" in self._metric_fn_list.keys()
            ):
                # then we are doing mutual info.
                # this stores the "dryrun" / unconditional answer loglikelihoods
                lls_unconditional = lls[1::2]
                if len(lls_unconditional) != len(choices):
                    raise ValueError
                # and this stores our "regular" conditional loglikelihoods
                lls = lls[::2]

            pred = np.argmax(lls)
            pred_norm = np.argmax(lls / completion_len)

            if self.multiple_input:
                gold = self.doc_to_text(doc)
            else:
                gold = self.doc_to_target(doc)

            gold_index_error = False
            if isinstance(gold, list):
                gold = [i if i < len(choices) else -100 for i in gold]
                if -100 in gold:
                    gold_index_error = True
            else:
                if isinstance(gold, int):
                    gold = gold if gold < len(choices) else -100
                elif isinstance(gold, str):
                    gold = choices.index(gold) if gold in choices else -100

                if gold == -100:
                    gold_index_error = True

            if gold_index_error:
                eval_logger.warning(
                    f"Label index was not in within range of available choices,"
                    f"Sample:\n\n{doc}\n\n"
                )

            if self.multiple_target:
                acc = 1.0 if pred in gold else 0.0
                acc_norm = 1.0 if pred_norm in gold else 0.0
                exact_match = int(any([is_greedy[i] if i != -100 else 0 for i in gold]))
            else:
                acc = 1.0 if pred == gold else 0.0
                acc_norm = 1.0 if pred_norm == gold else 0.0
                # TODO: this gets score of 0 on arc_challenge for pythia-70m. need to test that this works properly
                exact_match = int(is_greedy[gold]) if gold != -100 else 0

            prob_norm = utils.softmax(lls)

            # TODO use keyword arguments to the metric?
            # gold, pred, norm stuff, the original lls,
            result_dict = {
                **({"acc": acc} if "acc" in use_metric else {}),
                **({"f1": (gold, pred)} if "f1" in use_metric else {}),
                **({"mcc": (gold, pred)} if "mcc" in use_metric else {}),
                **({"acc_norm": acc_norm} if "acc_norm" in use_metric else {}),
                **({"exact_match": exact_match} if "exact_match" in use_metric else {}),
                **(
                    {"brier_score": (gold, prob_norm)}
                    if "brier_score" in use_metric
                    else {}
                ),
            }

            if "acc_mutual_info" in use_metric:
                lls_mutual_info = [
                    ll_c - ll_u for ll_c, ll_u in zip(lls, lls_unconditional)
                ]
                acc_mutual_info = 1.0 if np.argmax(lls_mutual_info) == gold else 0.0
                result_dict["acc_mutual_info"] = acc_mutual_info

        elif self.OUTPUT_TYPE == "generate_until":
            gold = self.doc_to_target(doc)
            result = results[0]
            if self.config.doc_to_choice is not None:
                # If you set doc_to_choice,
                # it assumes that doc_to_target returns a number.
                choices = self.doc_to_choice(doc)
                gold = choices[gold]
            # we expect multiple_targets to be a list.
            elif self.multiple_target:
                gold = list(gold)
            elif type(gold) != type(result):
                # cast gold to the same type as result
                gold = type(result)(gold)

            for metric in self._metric_fn_list.keys():
                if self.multiple_target:
                    # in the case where we have multiple targets,
                    # return true if any are true
                    # TODO: this may break for multipLe_target, non zero-or-1 metrics
                    scores = []
                    if not isinstance(gold, list):
                        # sometimes, a multiple_target dataset has exceptions where one doc has only one string answer
                        # print(gold)
                        gold = [gold]
                    if metric == "exact_match":
                        result = [result for _ in range(len(gold))]
                        scores = self._metric_fn_list[metric](
                            references=gold,
                            predictions=result,
                            **self._metric_fn_kwargs[metric],
                        )[metric]
                        result_score = 1.0 if scores > 0.0 else 0.0
                    else:
                        for gold_option in gold:
                            try:
                                result_score = self._metric_fn_list[metric](
                                    references=[gold_option],
                                    predictions=[result],
                                    **self._metric_fn_kwargs[metric],
                                )
                            except (
                                TypeError
                            ):  # TODO: this is hacky and I don't want to do it
                                result_score = self._metric_fn_list[metric](
                                    [gold_option, result]
                                )
                            if isinstance(result_score, dict):
                                # TODO: this handles the case where HF evaluate returns a dict.
                                result_score = result_score[metric]
                            scores.append(result_score)
                        if any(scores):
                            result_score = 1.0
                        else:
                            result_score = 0.0
                else:
                    try:
                        result_score = self._metric_fn_list[metric](
                            references=[gold],
                            predictions=[result],
                            **self._metric_fn_kwargs[metric],
                        )
                    except TypeError:  # needed for now in order to use a different interface between our own metrics and HF Evaluate metrics
                        result_score = self._metric_fn_list[metric]([gold, result])
                    if isinstance(result_score, dict):
                        # TODO: this handles the case where HF evaluate returns a dict.
                        result_score = result_score[metric]
                result_dict[metric] = result_score
        else:
            raise ValueError(
                f"Passed invalid output_type '{self.OUTPUT_TYPE}' ! Please use one of ",
                "'loglikelihood', 'loglikelihood_rolling', 'generate_until' or 'multiple_choice'",
            )

        return result_dict

    def aggregation(self) -> dict:
        return self._aggregation_list

    def higher_is_better(self) -> dict:
        return self._higher_is_better

    def get_config(self, key: str) -> Any:
        return getattr(self._config, key, None)

    def __repr__(self):
        return (
            f"ConfigurableTask(task_name={getattr(self.config, 'task', None)},"
            f"group_name={getattr(self.config, 'group', None)},"
            f"output_type={self.OUTPUT_TYPE},"
            f"num_fewshot={getattr(self.config, 'num_fewshot', None)},"
            f"num_samples={len(self.eval_docs)})"
        )


class MultipleChoiceTask(Task):
    OUTPUT_TYPE = "loglikelihood"

    def doc_to_target(self, doc: dict) -> str:
        return " " + doc["choices"][doc["gold"]]

    def construct_requests(self, doc: dict, ctx: str, **kwargs) -> List[Instance]:
        # TODO: add mutual info here?
        return [
            Instance(
                request_type="loglikelihood",
                doc=doc,
                arguments=(ctx, " {}".format(choice)),
                idx=i,
                **kwargs,
            )
            for i, choice in enumerate(doc["choices"])
        ]

    def process_results(self, doc: dict, results: Iterable[Tuple[float, bool]]) -> dict:
        results = [
            res[0] for res in results
        ]  # only retain loglikelihoods, discard is_greedy TODO: do we need is_greedy anywhere?
        gold = doc["gold"]

        acc = 1.0 if np.argmax(results) == gold else 0.0
        completion_len = np.array([float(len(i)) for i in doc["choices"]])
        acc_norm = 1.0 if np.argmax(results / completion_len) == gold else 0.0

        return {
            "acc": acc,
            "acc_norm": acc_norm,
        }

    def higher_is_better(self) -> dict:
        return {
            "acc": True,
            "acc_norm": True,
        }

    def aggregation(self) -> dict:
        return {
            "acc": mean,
            "acc_norm": mean,
        }


class PerplexityTask(Task):
    OUTPUT_TYPE = "loglikelihood_rolling"

    def has_training_docs(self) -> bool:
        return False

    def fewshot_examples(self, k: int, rnd) -> List:
        if k != 0:
            raise ValueError(
                "The number of fewshot examples must be 0 for perplexity tasks."
            )
        return []

    def fewshot_context(self, doc: dict, num_fewshot: int) -> Literal[""]:
        if num_fewshot != 0:
            raise ValueError(
                "The number of fewshot examples must be 0 for perplexity tasks."
            )

        return ""

    def higher_is_better(self) -> dict:
        return {
            "word_perplexity": False,
            "byte_perplexity": False,
            "bits_per_byte": False,
        }

    def doc_to_decontamination_query(self, doc):
        return doc

    def doc_to_text(self, doc) -> str:
        return ""

    def doc_to_target(self, doc):
        return doc

    def construct_requests(self, doc: dict, ctx: Optional[str], **kwargs):
        if bool(ctx):
            raise ValueError

        return Instance(
            request_type=self.OUTPUT_TYPE,
            doc=doc,
            arguments=(self.doc_to_target(doc),),
            idx=0,
            **kwargs,
        )

    def process_results(self, doc: dict, results: Tuple[float]) -> dict:
        (loglikelihood,) = results
        words = self.count_words(self.doc_to_target(doc))
        bytes_ = self.count_bytes(self.doc_to_target(doc))
        return {
            "word_perplexity": (loglikelihood, words),
            "byte_perplexity": (loglikelihood, bytes_),
            "bits_per_byte": (loglikelihood, bytes_),
        }

    def aggregation(self) -> dict:
        return {
            "word_perplexity": weighted_perplexity,
            "byte_perplexity": weighted_perplexity,
            "bits_per_byte": bits_per_byte,
        }

    @classmethod
    def count_bytes(cls, doc) -> int:
        return len(doc.encode("utf-8"))

    @classmethod
    def count_words(cls, doc) -> int:
        """Downstream tasks with custom word boundaries should override this!"""
        return len(re.split(r"\s+", doc))