flax ner example (#13365)

* flax ner example

* added task to README

* updated readme

* 1. ArgumentParser -> HfArgumentParser
2. step-wise logging,eval and save

* added requirements.txt

* added progress bar

* updated README

* added check_min_version

* updated training data permuattion with JAX

* added metric lib to requirements

* updated readme table

* fixed imports

examples/flax/token-classification/README.md

+<!---
+Copyright 2021 The Google Flax Team Authors and HuggingFace Team. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+-->
+
+# Token classification examples
+
+Fine-tuning the library models for token classification task such as Named Entity Recognition (NER), Parts-of-speech tagging (POS) or phrase extraction (CHUNKS). The main script run_flax_ner.py leverages the 🤗 Datasets library. You can easily customize it to your needs if you need extra processing on your datasets.
+
+It will either run on a datasets hosted on our hub or with your own text files for training and validation, you might just need to add some tweaks in the data preprocessing.
+
+The following example fine-tunes BERT on CoNLL-2003:
+
+To begin with it is recommended to create a model repository to save the trained model and logs.
+Here we call the model `"bert-ner-conll2003-test"`, but you can change the model name as you like.
+
+You can do this either directly on [huggingface.co](https://huggingface.co/new) (assuming that
+you are logged in) or via the command line:
+
+```
+huggingface-cli repo create bert-ner-conll2003-test
+```
+
+Next we clone the model repository to add the tokenizer and model files.
+
+```
+git clone https://huggingface.co/<your-username>/bert-ner-conll2003-test
+```
+
+Great, we have set up our model repository. During training, we will automatically
+push the training logs and model weights to the repo.
+
+Next, let's add a symbolic link to the `run_flax_ner.py`.
+
+```bash
+export MODEL_DIR="./bert-ner-conll2003-test"
+ln -s ~/transformers/examples/flax/token-classification/run_flax_ner.py run_flax_ner.py
+```
+
+```bash
+python run_flax_ner.py \
+  --model_name_or_path bert-base-cased \
+  --dataset_name conll2003 \
+  --max_seq_length 128 \
+  --learning_rate 2e-5 \
+  --num_train_epochs 3 \
+  --per_device_train_batch_size 4 \
+  --output_dir ${MODEL_DIR} \
+  --eval_steps 300 \
+  --push_to_hub
+```
+
+Using the command above, the script will train for 3 epochs and run eval after each epoch. 
+Metrics and hyperparameters are stored in Tensorflow event files in `--output_dir`.
+You can see the results by running `tensorboard` in that directory:
+
+```bash
+$ tensorboard --logdir .
+```
+
+or directly on the hub under *Training metrics*.
+
+sample Metrics - [tfhub.dev](https://tensorboard.dev/experiment/u52qsBIpQSKEEXEJd2LVYA)
\ No newline at end of file

examples/flax/token-classification/requirements.txt

+datasets >= 1.8.0
+jax>=0.2.8
+jaxlib>=0.1.59
+flax>=0.3.4
+optax>=0.0.8
+seqeval
\ No newline at end of file

examples/flax/token-classification/run_flax_ner.py

+#!/usr/bin/env python
+# coding=utf-8
+# Copyright 2021 The HuggingFace Inc. team. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+""" Fine-tuning a 🤗 Flax Transformers model on token classification tasks (NER, POS, CHUNKS)"""
+import logging
+import os
+import random
+import sys
+import time
+from dataclasses import dataclass, field
+from itertools import chain
+from typing import Any, Callable, Dict, Optional, Tuple
+
+import datasets
+import numpy as np
+from datasets import ClassLabel, load_dataset, load_metric
+from tqdm import tqdm
+
+import jax
+import jax.numpy as jnp
+import optax
+import transformers
+from flax import struct, traverse_util
+from flax.jax_utils import replicate, unreplicate
+from flax.metrics import tensorboard
+from flax.training import train_state
+from flax.training.common_utils import get_metrics, onehot, shard
+from transformers import (
+    AutoConfig,
+    AutoTokenizer,
+    FlaxAutoModelForTokenClassification,
+    HfArgumentParser,
+    TrainingArguments,
+)
+from transformers.utils import check_min_version
+from transformers.utils.versions import require_version
+
+
+logger = logging.getLogger(__name__)
+# Will error if the minimal version of Transformers is not installed. Remove at your own risks.
+check_min_version("4.11.0.dev0")
+
+require_version("datasets>=1.8.0", "To fix: pip install -r examples/pytorch/token-classification/requirements.txt")
+
+Array = Any
+Dataset = datasets.arrow_dataset.Dataset
+PRNGKey = Any
+
+
+@dataclass
+class ModelArguments:
+    """
+    Arguments pertaining to which model/config/tokenizer we are going to fine-tune from.
+    """
+
+    model_name_or_path: str = field(
+        metadata={"help": "Path to pretrained model or model identifier from huggingface.co/models"}
+    )
+    config_name: Optional[str] = field(
+        default=None, metadata={"help": "Pretrained config name or path if not the same as model_name"}
+    )
+    tokenizer_name: Optional[str] = field(
+        default=None, metadata={"help": "Pretrained tokenizer name or path if not the same as model_name"}
+    )
+    cache_dir: Optional[str] = field(
+        default=None,
+        metadata={"help": "Where do you want to store the pretrained models downloaded from huggingface.co"},
+    )
+    model_revision: str = field(
+        default="main",
+        metadata={"help": "The specific model version to use (can be a branch name, tag name or commit id)."},
+    )
+    use_auth_token: bool = field(
+        default=False,
+        metadata={
+            "help": "Will use the token generated when running `transformers-cli login` (necessary to use this script "
+            "with private models)."
+        },
+    )
+
+
+@dataclass
+class DataTrainingArguments:
+    """
+    Arguments pertaining to what data we are going to input our model for training and eval.
+    """
+
+    task_name: Optional[str] = field(default="ner", metadata={"help": "The name of the task (ner, pos...)."})
+    dataset_name: Optional[str] = field(
+        default=None, metadata={"help": "The name of the dataset to use (via the datasets library)."}
+    )
+    dataset_config_name: Optional[str] = field(
+        default=None, metadata={"help": "The configuration name of the dataset to use (via the datasets library)."}
+    )
+    train_file: Optional[str] = field(
+        default=None, metadata={"help": "The input training data file (a csv or JSON file)."}
+    )
+    validation_file: Optional[str] = field(
+        default=None,
+        metadata={"help": "An optional input evaluation data file to evaluate on (a csv or JSON file)."},
+    )
+    test_file: Optional[str] = field(
+        default=None,
+        metadata={"help": "An optional input test data file to predict on (a csv or JSON file)."},
+    )
+    text_column_name: Optional[str] = field(
+        default=None, metadata={"help": "The column name of text to input in the file (a csv or JSON file)."}
+    )
+    label_column_name: Optional[str] = field(
+        default=None, metadata={"help": "The column name of label to input in the file (a csv or JSON file)."}
+    )
+    overwrite_cache: bool = field(
+        default=False, metadata={"help": "Overwrite the cached training and evaluation sets"}
+    )
+    preprocessing_num_workers: Optional[int] = field(
+        default=None,
+        metadata={"help": "The number of processes to use for the preprocessing."},
+    )
+    max_seq_length: int = field(
+        default=None,
+        metadata={
+            "help": "The maximum total input sequence length after tokenization. If set, sequences longer "
+            "than this will be truncated, sequences shorter will be padded."
+        },
+    )
+    max_train_samples: Optional[int] = field(
+        default=None,
+        metadata={
+            "help": "For debugging purposes or quicker training, truncate the number of training examples to this "
+            "value if set."
+        },
+    )
+    max_eval_samples: Optional[int] = field(
+        default=None,
+        metadata={
+            "help": "For debugging purposes or quicker training, truncate the number of evaluation examples to this "
+            "value if set."
+        },
+    )
+    max_predict_samples: Optional[int] = field(
+        default=None,
+        metadata={
+            "help": "For debugging purposes or quicker training, truncate the number of prediction examples to this "
+            "value if set."
+        },
+    )
+    label_all_tokens: bool = field(
+        default=False,
+        metadata={
+            "help": "Whether to put the label for one word on all tokens of generated by that word or just on the "
+            "one (in which case the other tokens will have a padding index)."
+        },
+    )
+    return_entity_level_metrics: bool = field(
+        default=False,
+        metadata={"help": "Whether to return all the entity levels during evaluation or just the overall ones."},
+    )
+
+    def __post_init__(self):
+        if self.dataset_name is None and self.train_file is None and self.validation_file is None:
+            raise ValueError("Need either a dataset name or a training/validation file.")
+        else:
+            if self.train_file is not None:
+                extension = self.train_file.split(".")[-1]
+                assert extension in ["csv", "json"], "`train_file` should be a csv or a json file."
+            if self.validation_file is not None:
+                extension = self.validation_file.split(".")[-1]
+                assert extension in ["csv", "json"], "`validation_file` should be a csv or a json file."
+        self.task_name = self.task_name.lower()
+
+
+def create_train_state(
+    model: FlaxAutoModelForTokenClassification,
+    learning_rate_fn: Callable[[int], float],
+    num_labels: int,
+    training_args: TrainingArguments,
+) -> train_state.TrainState:
+    """Create initial training state."""
+
+    class TrainState(train_state.TrainState):
+        """Train state with an Optax optimizer.
+
+        The two functions below differ depending on whether the task is classification
+        or regression.
+
+        Args:
+          logits_fn: Applied to last layer to obtain the logits.
+          loss_fn: Function to compute the loss.
+        """
+
+        logits_fn: Callable = struct.field(pytree_node=False)
+        loss_fn: Callable = struct.field(pytree_node=False)
+
+    # We use Optax's "masking" functionality to not apply weight decay
+    # to bias and LayerNorm scale parameters. decay_mask_fn returns a
+    # mask boolean with the same structure as the parameters.
+    # The mask is True for parameters that should be decayed.
+    # Note that this mask is specifically adapted for FlaxBERT-like models.
+    # For other models, one should correct the layer norm parameter naming
+    # accordingly.
+    def decay_mask_fn(params):
+        flat_params = traverse_util.flatten_dict(params)
+        flat_mask = {path: (path[-1] != "bias" and path[-2:] != ("LayerNorm", "scale")) for path in flat_params}
+        return traverse_util.unflatten_dict(flat_mask)
+
+    tx = optax.adamw(
+        learning_rate=learning_rate_fn,
+        b1=training_args.adam_beta1,
+        b2=training_args.adam_beta2,
+        eps=training_args.adam_epsilon,
+        weight_decay=training_args.weight_decay,
+        mask=decay_mask_fn,
+    )
+
+    def cross_entropy_loss(logits, labels):
+        xentropy = optax.softmax_cross_entropy(logits, onehot(labels, num_classes=num_labels))
+        return jnp.mean(xentropy)
+
+    return TrainState.create(
+        apply_fn=model.__call__,
+        params=model.params,
+        tx=tx,
+        logits_fn=lambda logits: logits.argmax(-1),
+        loss_fn=cross_entropy_loss,
+    )
+
+
+def create_learning_rate_fn(
+    train_ds_size: int, train_batch_size: int, num_train_epochs: int, num_warmup_steps: int, learning_rate: float
+) -> Callable[[int], jnp.array]:
+    """Returns a linear warmup, linear_decay learning rate function."""
+    steps_per_epoch = train_ds_size // train_batch_size
+    num_train_steps = steps_per_epoch * num_train_epochs
+    warmup_fn = optax.linear_schedule(init_value=0.0, end_value=learning_rate, transition_steps=num_warmup_steps)
+    decay_fn = optax.linear_schedule(
+        init_value=learning_rate, end_value=0, transition_steps=num_train_steps - num_warmup_steps
+    )
+    schedule_fn = optax.join_schedules(schedules=[warmup_fn, decay_fn], boundaries=[num_warmup_steps])
+    return schedule_fn
+
+
+def train_data_collator(rng: PRNGKey, dataset: Dataset, batch_size: int):
+    """Returns shuffled batches of size `batch_size` from truncated `train dataset`, sharded over all local devices."""
+    steps_per_epoch = len(dataset) // batch_size
+    perms = jax.random.permutation(rng, len(dataset))
+    perms = perms[: steps_per_epoch * batch_size]  # Skip incomplete batch.
+    perms = perms.reshape((steps_per_epoch, batch_size))
+
+    for perm in perms:
+        batch = dataset[perm]
+        batch = {k: np.array(v) for k, v in batch.items()}
+        batch = shard(batch)
+
+        yield batch
+
+
+def eval_data_collator(dataset: Dataset, batch_size: int):
+    """Returns batches of size `batch_size` from `eval dataset`, sharded over all local devices."""
+    for i in range(len(dataset) // batch_size):
+        batch = dataset[i * batch_size : (i + 1) * batch_size]
+        batch = {k: np.array(v) for k, v in batch.items()}
+        batch = shard(batch)
+
+        yield batch
+
+
+def main():
+    # See all possible arguments in src/transformers/training_args.py
+    # or by passing the --help flag to this script.
+    # We now keep distinct sets of args, for a cleaner separation of concerns.
+
+    parser = HfArgumentParser((ModelArguments, DataTrainingArguments, TrainingArguments))
+    if len(sys.argv) == 2 and sys.argv[1].endswith(".json"):
+        # If we pass only one argument to the script and it's the path to a json file,
+        # let's parse it to get our arguments.
+        model_args, data_args, training_args = parser.parse_json_file(json_file=os.path.abspath(sys.argv[1]))
+    else:
+        model_args, data_args, training_args = parser.parse_args_into_dataclasses()
+
+    # Make one log on every process with the configuration for debugging.
+    logging.basicConfig(
+        format="%(asctime)s - %(levelname)s - %(name)s - %(message)s",
+        datefmt="%m/%d/%Y %H:%M:%S",
+        level=logging.INFO,
+    )
+    # Setup logging, we only want one process per machine to log things on the screen.
+    logger.setLevel(logging.INFO if jax.process_index() == 0 else logging.ERROR)
+    if jax.process_index() == 0:
+        datasets.utils.logging.set_verbosity_warning()
+        transformers.utils.logging.set_verbosity_info()
+    else:
+        datasets.utils.logging.set_verbosity_error()
+        transformers.utils.logging.set_verbosity_error()
+
+    # Get the datasets: you can either provide your own CSV/JSON/TXT training and evaluation files (see below)
+    # or just provide the name of one of the public datasets for token classification task available on the hub at https://huggingface.co/datasets/
+    # (the dataset will be downloaded automatically from the datasets Hub).
+    #
+    # For CSV/JSON files, this script will use the column called 'tokens' or the first column if no column called
+    # 'tokens' is found. You can easily tweak this behavior (see below).
+    #
+    # In distributed training, the load_dataset function guarantee that only one local process can concurrently
+    # download the dataset.
+    if data_args.dataset_name is not None:
+        # Downloading and loading a dataset from the hub.
+        raw_datasets = load_dataset(
+            data_args.dataset_name, data_args.dataset_config_name, cache_dir=model_args.cache_dir
+        )
+    else:
+        # Loading the dataset from local csv or json file.
+        data_files = {}
+        if data_args.train_file is not None:
+            data_files["train"] = data_args.train_file
+        if data_args.validation_file is not None:
+            data_files["validation"] = data_args.validation_file
+        extension = (data_args.train_file if data_args.train_file is not None else data_args.valid_file).split(".")[-1]
+        raw_datasets = load_dataset(extension, data_files=data_files, cache_dir=model_args.cache_dir)
+    # See more about loading any type of standard or custom dataset at
+    # https://huggingface.co/docs/datasets/loading_datasets.html.
+
+    if raw_datasets["train"] is not None:
+        column_names = raw_datasets["train"].column_names
+        features = raw_datasets["train"].features
+    else:
+        column_names = raw_datasets["validation"].column_names
+        features = raw_datasets["validation"].features
+
+    if data_args.text_column_name is not None:
+        text_column_name = data_args.text_column_name
+    elif "tokens" in column_names:
+        text_column_name = "tokens"
+    else:
+        text_column_name = column_names[0]
+
+    if data_args.label_column_name is not None:
+        label_column_name = data_args.label_column_name
+    elif f"{data_args.task_name}_tags" in column_names:
+        label_column_name = f"{data_args.task_name}_tags"
+    else:
+        label_column_name = column_names[1]
+
+    # In the event the labels are not a `Sequence[ClassLabel]`, we will need to go through the dataset to get the
+    # unique labels.
+    def get_label_list(labels):
+        unique_labels = set()
+        for label in labels:
+            unique_labels = unique_labels | set(label)
+        label_list = list(unique_labels)
+        label_list.sort()
+        return label_list
+
+    if isinstance(features[label_column_name].feature, ClassLabel):
+        label_list = features[label_column_name].feature.names
+        # No need to convert the labels since they are already ints.
+        label_to_id = {i: i for i in range(len(label_list))}
+    else:
+        label_list = get_label_list(raw_datasets["train"][label_column_name])
+        label_to_id = {l: i for i, l in enumerate(label_list)}
+    num_labels = len(label_list)
+
+    # Load pretrained model and tokenizer
+    config = AutoConfig.from_pretrained(
+        model_args.config_name if model_args.config_name else model_args.model_name_or_path,
+        num_labels=num_labels,
+        label2id=label_to_id,
+        id2label={i: l for l, i in label_to_id.items()},
+        finetuning_task=data_args.task_name,
+        cache_dir=model_args.cache_dir,
+        revision=model_args.model_revision,
+        use_auth_token=True if model_args.use_auth_token else None,
+    )
+    tokenizer_name_or_path = model_args.tokenizer_name if model_args.tokenizer_name else model_args.model_name_or_path
+    if config.model_type in {"gpt2", "roberta"}:
+        tokenizer = AutoTokenizer.from_pretrained(
+            tokenizer_name_or_path,
+            cache_dir=model_args.cache_dir,
+            revision=model_args.model_revision,
+            use_auth_token=True if model_args.use_auth_token else None,
+            add_prefix_space=True,
+        )
+    else:
+        tokenizer = AutoTokenizer.from_pretrained(
+            tokenizer_name_or_path,
+            cache_dir=model_args.cache_dir,
+            revision=model_args.model_revision,
+            use_auth_token=True if model_args.use_auth_token else None,
+        )
+    model = FlaxAutoModelForTokenClassification.from_pretrained(
+        model_args.model_name_or_path,
+        config=config,
+        cache_dir=model_args.cache_dir,
+        revision=model_args.model_revision,
+        use_auth_token=True if model_args.use_auth_token else None,
+    )
+
+    # Preprocessing the datasets
+    # Tokenize all texts and align the labels with them.
+    def tokenize_and_align_labels(examples):
+        tokenized_inputs = tokenizer(
+            examples[text_column_name],
+            max_length=data_args.max_seq_length,
+            padding="max_length",
+            truncation=True,
+            # We use this argument because the texts in our dataset are lists of words (with a label for each word).
+            is_split_into_words=True,
+        )
+
+        labels = []
+
+        for i, label in enumerate(examples[label_column_name]):
+            word_ids = tokenized_inputs.word_ids(batch_index=i)
+            previous_word_idx = None
+            label_ids = []
+            for word_idx in word_ids:
+                # Special tokens have a word id that is None. We set the label to -100 so they are automatically
+                # ignored in the loss function.
+                if word_idx is None:
+                    label_ids.append(-100)
+                # We set the label for the first token of each word.
+                elif word_idx != previous_word_idx:
+                    label_ids.append(label_to_id[label[word_idx]])
+                # For the other tokens in a word, we set the label to either the current label or -100, depending on
+                # the label_all_tokens flag.
+                else:
+                    label_ids.append(label_to_id[label[word_idx]] if data_args.label_all_tokens else -100)
+                previous_word_idx = word_idx
+
+            labels.append(label_ids)
+        tokenized_inputs["labels"] = labels
+        return tokenized_inputs
+
+    processed_raw_datasets = raw_datasets.map(
+        tokenize_and_align_labels,
+        batched=True,
+        num_proc=data_args.preprocessing_num_workers,
+        load_from_cache_file=not data_args.overwrite_cache,
+        remove_columns=raw_datasets["train"].column_names,
+        desc="Running tokenizer on dataset",
+    )
+
+    train_dataset = processed_raw_datasets["train"]
+    eval_dataset = processed_raw_datasets["validation"]
+
+    # Log a few random samples from the training set:
+    for index in random.sample(range(len(train_dataset)), 3):
+        logger.info(f"Sample {index} of the training set: {train_dataset[index]}.")
+
+    # Define a summary writer
+    summary_writer = tensorboard.SummaryWriter(training_args.output_dir)
+    summary_writer.hparams({**training_args.to_dict(), **vars(model_args), **vars(data_args)})
+
+    def write_train_metric(summary_writer, train_metrics, train_time, step):
+        summary_writer.scalar("train_time", train_time, step)
+
+        train_metrics = get_metrics(train_metrics)
+        for key, vals in train_metrics.items():
+            tag = f"train_{key}"
+            for i, val in enumerate(vals):
+                summary_writer.scalar(tag, val, step - len(vals) + i + 1)
+
+    def write_eval_metric(summary_writer, eval_metrics, step):
+        for metric_name, value in eval_metrics.items():
+            summary_writer.scalar(f"eval_{metric_name}", value, step)
+
+    num_epochs = int(training_args.num_train_epochs)
+    rng = jax.random.PRNGKey(training_args.seed)
+    dropout_rngs = jax.random.split(rng, jax.local_device_count())
+
+    train_batch_size = training_args.per_device_train_batch_size * jax.local_device_count()
+    eval_batch_size = training_args.per_device_eval_batch_size * jax.local_device_count()
+
+    learning_rate_fn = create_learning_rate_fn(
+        len(train_dataset),
+        train_batch_size,
+        training_args.num_train_epochs,
+        training_args.warmup_steps,
+        training_args.learning_rate,
+    )
+
+    state = create_train_state(model, learning_rate_fn, num_labels=num_labels, training_args=training_args)
+
+    # define step functions
+    def train_step(
+        state: train_state.TrainState, batch: Dict[str, Array], dropout_rng: PRNGKey
+    ) -> Tuple[train_state.TrainState, float]:
+        """Trains model with an optimizer (both in `state`) on `batch`, returning a pair `(new_state, loss)`."""
+        dropout_rng, new_dropout_rng = jax.random.split(dropout_rng)
+        targets = batch.pop("labels")
+
+        def loss_fn(params):
+            logits = state.apply_fn(**batch, params=params, dropout_rng=dropout_rng, train=True)[0]
+            loss = state.loss_fn(logits, targets)
+            return loss
+
+        grad_fn = jax.value_and_grad(loss_fn)
+        loss, grad = grad_fn(state.params)
+        grad = jax.lax.pmean(grad, "batch")
+        new_state = state.apply_gradients(grads=grad)
+        metrics = jax.lax.pmean({"loss": loss, "learning_rate": learning_rate_fn(state.step)}, axis_name="batch")
+        return new_state, metrics, new_dropout_rng
+
+    p_train_step = jax.pmap(train_step, axis_name="batch", donate_argnums=(0,))
+
+    def eval_step(state, batch):
+        logits = state.apply_fn(**batch, params=state.params, train=False)[0]
+        return state.logits_fn(logits)
+
+    p_eval_step = jax.pmap(eval_step, axis_name="batch")
+
+    metric = load_metric("seqeval")
+
+    def get_labels(y_pred, y_true):
+        # Transform predictions and references tensos to numpy arrays
+
+        # Remove ignored index (special tokens)
+        true_predictions = [
+            [label_list[p] for (p, l) in zip(pred, gold_label) if l != -100]
+            for pred, gold_label in zip(y_pred, y_true)
+        ]
+        true_labels = [
+            [label_list[l] for (p, l) in zip(pred, gold_label) if l != -100]
+            for pred, gold_label in zip(y_pred, y_true)
+        ]
+        return true_predictions, true_labels
+
+    def compute_metrics():
+        results = metric.compute()
+        if data_args.return_entity_level_metrics:
+            # Unpack nested dictionaries
+            final_results = {}
+            for key, value in results.items():
+                if isinstance(value, dict):
+                    for n, v in value.items():
+                        final_results[f"{key}_{n}"] = v
+                else:
+                    final_results[key] = value
+            return final_results
+        else:
+            return {
+                "precision": results["overall_precision"],
+                "recall": results["overall_recall"],
+                "f1": results["overall_f1"],
+                "accuracy": results["overall_accuracy"],
+            }
+
+    logger.info(f"===== Starting training ({num_epochs} epochs) =====")
+    train_time = 0
+
+    # make sure weights are replicated on each device
+    state = replicate(state)
+
+    train_time = 0
+    step_per_epoch = len(train_dataset) // train_batch_size
+    total_steps = step_per_epoch * num_epochs
+    epochs = tqdm(range(num_epochs), desc=f"Epoch ... (1/{num_epochs})", position=0)
+    for epoch in epochs:
+
+        train_start = time.time()
+        train_metrics = []
+
+        # Create sampling rng
+        rng, input_rng = jax.random.split(rng)
+
+        # train
+        for step, batch in enumerate(
+            tqdm(
+                train_data_collator(input_rng, train_dataset, train_batch_size),
+                total=step_per_epoch,
+                desc="Training...",
+                position=1,
+            )
+        ):
+            state, train_metric, dropout_rngs = p_train_step(state, batch, dropout_rngs)
+            train_metrics.append(train_metric)
+
+            cur_step = epoch * step_per_epoch + step
+
+            if cur_step % training_args.logging_steps == 0 and cur_step > 0:
+                # Save metrics
+                train_metric = unreplicate(train_metric)
+                train_time += time.time() - train_start
+                if jax.process_index() == 0:
+                    write_train_metric(summary_writer, train_metrics, train_time, cur_step)
+
+                epochs.write(
+                    f"Step... ({cur_step}/{total_steps} | Training Loss: {train_metric['loss']}, Learning Rate: {train_metric['learning_rate']})"
+                )
+
+                train_metrics = []
+
+            if cur_step % training_args.eval_steps == 0 and cur_step > 0:
+
+                eval_metrics = {}
+                # evaluate
+                for batch in tqdm(
+                    eval_data_collator(eval_dataset, eval_batch_size),
+                    total=len(eval_dataset) // eval_batch_size,
+                    desc="Evaluating ...",
+                    position=2,
+                ):
+                    labels = batch.pop("labels")
+                    predictions = p_eval_step(state, batch)
+                    predictions = np.array([pred for pred in chain(*predictions)])
+                    labels = np.array([label for label in chain(*labels)])
+                    labels[np.array(chain(*batch["attention_mask"])) == 0] = -100
+                    preds, refs = get_labels(predictions, labels)
+                    metric.add_batch(
+                        predictions=preds,
+                        references=refs,
+                    )
+
+                # evaluate also on leftover examples (not divisible by batch_size)
+                num_leftover_samples = len(eval_dataset) % eval_batch_size
+
+                # make sure leftover batch is evaluated on one device
+                if num_leftover_samples > 0 and jax.process_index() == 0:
+                    # take leftover samples
+                    batch = eval_dataset[-num_leftover_samples:]
+                    batch = {k: np.array(v) for k, v in batch.items()}
+
+                    labels = batch.pop("labels")
+                    predictions = eval_step(unreplicate(state), batch)
+                    labels = np.array(labels)
+                    labels[np.array(batch["attention_mask"]) == 0] = -100
+                    preds, refs = get_labels(predictions, labels)
+                    metric.add_batch(
+                        predictions=preds,
+                        references=refs,
+                    )
+
+                eval_metrics = compute_metrics()
+
+                if data_args.return_entity_level_metrics:
+                    logger.info(f"Step... ({cur_step}/{total_steps} | Validation metrics: {eval_metrics}")
+                else:
+                    logger.info(
+                        f"Step... ({cur_step}/{total_steps} | Validation f1: {eval_metrics['f1']}, Validation Acc: {eval_metrics['accuracy']})"
+                    )
+
+                if jax.process_index() == 0:
+                    write_eval_metric(summary_writer, eval_metrics, cur_step)
+
+            if (cur_step % training_args.save_steps == 0 and cur_step > 0) or (cur_step == total_steps):
+                # save checkpoint after each epoch and push checkpoint to the hub
+                if jax.process_index() == 0:
+                    params = jax.device_get(unreplicate(state.params))
+                    model.save_pretrained(
+                        training_args.output_dir,
+                        params=params,
+                        push_to_hub=training_args.push_to_hub,
+                        commit_message=f"Saving weights and logs of step {cur_step}",
+                    )
+        epochs.desc = f"Epoch ... {epoch + 1}/{num_epochs}"
+
+
+if __name__ == "__main__":
+    main()