Pipeline doc (#3055)

* Pipeline doc initial commit

* pipeline abstraction

* Remove modelcard argument from pipeline

* Task-specific pipelines can be instantiated with no model or tokenizer

* All pipelines doc

docs/source/index.rst

@@ -80,6 +80,7 @@ The library currently contains PyTorch and Tensorflow implementations, pre-train
     main_classes/configuration
     main_classes/model
     main_classes/tokenizer
+    main_classes/pipelines
     main_classes/optimizer_schedules
     main_classes/processors
 

docs/source/main_classes/pipelines.rst

+Pipelines
+----------------------------------------------------
+
+The pipelines are a great and easy way to use models for inference. These pipelines are objects that abstract most
+of the complex code from the library, offering a simple API dedicated to several tasks, including Named Entity
+Recognition, Masked Language Modeling, Sentiment Analysis, Feature Extraction and Question Answering.
+
+There are two categories of pipeline abstractions to be aware about:
+
+- The :class:`~transformers.pipeline` which is the most powerful object encapsulating all other pipelines
+- The other task-specific pipelines, such as :class:`~transformers.NerPipeline`
+  or :class:`~transformers.QuestionAnsweringPipeline`
+
+The pipeline abstraction
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The `pipeline` abstraction is a wrapper around all the other available pipelines. It is instantiated as any
+other pipeline but requires an additional argument which is the `task`.
+
+.. autoclass:: transformers.pipeline
+    :members:
+
+
+The task specific pipelines
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Parent class: Pipeline
+=========================================
+
+.. autoclass:: transformers.Pipeline
+    :members: predict, transform, save_pretrained
+
+NerPipeline
+==========================================
+
+.. autoclass:: transformers.NerPipeline
+
+TokenClassificationPipeline
+==========================================
+
+This class is an alias of the :class:`~transformers.NerPipeline` defined above. Please refer to that pipeline for
+documentation and usage examples.
+
+FillMaskPipeline
+==========================================
+
+.. autoclass:: transformers.FillMaskPipeline
+
+FeatureExtractionPipeline
+==========================================
+
+.. autoclass:: transformers.FeatureExtractionPipeline
+
+TextClassificationPipeline
+==========================================
+
+.. autoclass:: transformers.TextClassificationPipeline
+
+QuestionAnsweringPipeline
+==========================================
+
+.. autoclass:: transformers.QuestionAnsweringPipeline
+

src/transformers/pipelines.py

@@ -279,6 +279,9 @@ class _ScikitCompat(ABC):
 
 class Pipeline(_ScikitCompat):
     """
+    The Pipeline class is the class from which all pipelines inherit. Refer to this class for methods shared across
+    different pipelines.
+
     Base class implementing pipelined operations.
     Pipeline workflow is defined as a sequence of the following operations:
         Input -> Tokenization -> Model Inference -> Post-Processing (Task dependent) -> Output
@@ -292,39 +295,49 @@ class Pipeline(_ScikitCompat):
     pickle format.
 
     Arguments:
-        **model**: ``(str, PretrainedModel, TFPretrainedModel)``:
-            Reference to the model to use through this pipeline.
-
-        **tokenizer**: ``(str, PreTrainedTokenizer)``:
-            Reference to the tokenizer to use through this pipeline.
-
-        **args_parser**: ``ArgumentHandler``:
+        model (:obj:`str` or :obj:`~transformers.PreTrainedModel` or :obj:`~transformers.TFPreTrainedModel`, `optional`, defaults to :obj:`None`):
+            The model that will be used by the pipeline to make predictions. This can be :obj:`None`, a string
+            checkpoint identifier or an actual pre-trained model inheriting from
+            :class:`~transformers.PreTrainedModel` for PyTorch and :class:`~transformers.TFPreTrainedModel` for
+            TensorFlow.
+
+            If :obj:`None`, the default of the pipeline will be loaded.
+        tokenizer (:obj:`str` or :obj:`~transformers.PreTrainedTokenizer`, `optional`, defaults to :obj:`None`):
+            The tokenizer that will be used by the pipeline to encode data for the model. This can be :obj:`None`,
+            a string checkpoint identifier or an actual pre-trained tokenizer inheriting from
+            :class:`~transformers.PreTrainedTokenizer`.
+
+            If :obj:`None`, the default of the pipeline will be loaded.
+        modelcard (:obj:`str` or :class:`~transformers.ModelCard`, `optional`, defaults to :obj:`None`):
+            Model card attributed to the model for this pipeline.
+        framework (:obj:`str`, `optional`, defaults to :obj:`None`):
+            The framework to use, either "pt" for PyTorch or "tf" for TensorFlow. The specified framework must be
+            installed.
+
+            If no framework is specified, will default to the one currently installed. If no framework is specified
+            and both frameworks are installed, will default to PyTorch.
+        args_parser (:class:`~transformers.pipelines.ArgumentHandler`, `optional`, defaults to :obj:`None`):
             Reference to the object in charge of parsing supplied pipeline parameters.
-
-        **device**: ``int``:
+        device (:obj:`int`, `optional`, defaults to :obj:`-1`):
             Device ordinal for CPU/GPU supports. Setting this to -1 will leverage CPU, >=0 will run the model
             on the associated CUDA device id.
-
-        **binary_output** ``bool`` (default: False):
+        binary_output (:obj:`bool`, `optional`, defaults to :obj:`False`):
             Flag indicating if the output the pipeline should happen in a binary format (i.e. pickle) or as raw text.
 
     Return:
+        :obj:`List` or :obj:`Dict`:
         Pipeline returns list or dictionary depending on:
-         - Does the user provided multiple sample
-         - The pipeline expose multiple fields in the output object
-
-    Examples:
-        nlp = pipeline('ner')
-        nlp = pipeline('ner', model='...', config='...', tokenizer='...')
-        nlp = NerPipeline(model='...', config='...', tokenizer='...')
-        nlp = QuestionAnsweringPipeline(model=AutoModel.from_pretrained('...'), tokenizer='...')
+
+         - Whether the user supplied multiple samples
+         - Whether the pipeline exposes multiple fields in the output object
     """
 
     default_input_names = None
+    task = None
 
     def __init__(
         self,
-        model,
+        model: Optional = None,
         tokenizer: PreTrainedTokenizer = None,
         modelcard: Optional[ModelCard] = None,
         framework: Optional[str] = None,
@@ -336,6 +349,8 @@ class Pipeline(_ScikitCompat):
         if framework is None:
             framework = get_framework()
 
+        model, tokenizer = self.get_defaults(model, tokenizer, framework)
+
         self.model = model
         self.tokenizer = tokenizer
         self.modelcard = modelcard
@@ -467,15 +482,74 @@ class Pipeline(_ScikitCompat):
         else:
             return predictions.numpy()
 
+    def get_defaults(self, model, tokenizer, framework):
+        task_defaults = SUPPORTED_TASKS[self.task]
+        if model is None:
+            if framework == "tf":
+                model = task_defaults["tf"].from_pretrained(task_defaults["default"]["model"]["tf"])
+            elif framework == "pt":
+                model = task_defaults["pt"].from_pretrained(task_defaults["default"]["model"]["pt"])
+            else:
+                raise ValueError("Provided framework should be either 'tf' for TensorFlow or 'pt' for PyTorch.")
+
+        if tokenizer is None:
+            default_tokenizer = task_defaults["default"]["tokenizer"]
+            if isinstance(default_tokenizer, tuple):
+                # For tuple we have (tokenizer name, {kwargs})
+                tokenizer = AutoTokenizer.from_pretrained(default_tokenizer[0], **default_tokenizer[1])
+            else:
+                tokenizer = AutoTokenizer.from_pretrained(default_tokenizer)
+
+        return model, tokenizer
+
 
 class FeatureExtractionPipeline(Pipeline):
     """
-    Feature extraction pipeline using Model head.
+    Feature extraction pipeline using Model head. This pipeline extracts the hidden states from the base transformer,
+    which can be used as features in a downstream tasks.
+
+    This feature extraction pipeline can currently be loaded from the :func:`~transformers.pipeline` method using
+    the following task identifier(s):
+
+    - "feature-extraction", for extracting features of a sequence.
+
+    All models may be used for this pipeline. See a list of all models, including community-contributed models on
+    `huggingface.co/models <https://huggingface.co/models>`__.
+
+    Arguments:
+        model (:obj:`str` or :obj:`~transformers.PreTrainedModel` or :obj:`~transformers.TFPreTrainedModel`, `optional`, defaults to :obj:`None`):
+            The model that will be used by the pipeline to make predictions. This can be :obj:`None`, a string
+            checkpoint identifier or an actual pre-trained model inheriting from
+            :class:`~transformers.PreTrainedModel` for PyTorch and :class:`~transformers.TFPreTrainedModel` for
+            TensorFlow.
+
+            If :obj:`None`, the default of the pipeline will be loaded.
+        tokenizer (:obj:`str` or :obj:`~transformers.PreTrainedTokenizer`, `optional`, defaults to :obj:`None`):
+            The tokenizer that will be used by the pipeline to encode data for the model. This can be :obj:`None`,
+            a string checkpoint identifier or an actual pre-trained tokenizer inheriting from
+            :class:`~transformers.PreTrainedTokenizer`.
+
+            If :obj:`None`, the default of the pipeline will be loaded.
+        modelcard (:obj:`str` or :class:`~transformers.ModelCard`, `optional`, defaults to :obj:`None`):
+            Model card attributed to the model for this pipeline.
+        framework (:obj:`str`, `optional`, defaults to :obj:`None`):
+            The framework to use, either "pt" for PyTorch or "tf" for TensorFlow. The specified framework must be
+            installed.
+
+            If no framework is specified, will default to the one currently installed. If no framework is specified
+            and both frameworks are installed, will default to PyTorch.
+        args_parser (:class:`~transformers.pipelines.ArgumentHandler`, `optional`, defaults to :obj:`None`):
+            Reference to the object in charge of parsing supplied pipeline parameters.
+        device (:obj:`int`, `optional`, defaults to :obj:`-1`):
+            Device ordinal for CPU/GPU supports. Setting this to -1 will leverage CPU, >=0 will run the model
+            on the associated CUDA device id.
     """
 
+    task = "feature-extraction"
+
     def __init__(
         self,
-        model,
+        model: Optional = None,
         tokenizer: PreTrainedTokenizer = None,
         modelcard: Optional[ModelCard] = None,
         framework: Optional[str] = None,
@@ -498,9 +572,49 @@ class FeatureExtractionPipeline(Pipeline):
 
 class TextClassificationPipeline(Pipeline):
     """
-    Text classification pipeline using ModelForTextClassification head.
+    Text classification pipeline using ModelForSequenceClassification head. See the
+    `sequence classification usage <../usage.html#sequence-classification>`__ examples for more information.
+
+    This text classification pipeline can currently be loaded from the :func:`~transformers.pipeline` method using
+    the following task identifier(s):
+
+    - "sentiment-analysis", for classifying sequences according to positive or negative sentiments.
+
+    The models that this pipeline can use are models that have been fine-tuned on a sequence classification task.
+    See the list of available community models fine-tuned on such a task on
+    `huggingface.co/models <https://huggingface.co/models?search=&filter=text-classification>`__.
+
+    Arguments:
+        model (:obj:`str` or :obj:`~transformers.PreTrainedModel` or :obj:`~transformers.TFPreTrainedModel`, `optional`, defaults to :obj:`None`):
+            The model that will be used by the pipeline to make predictions. This can be :obj:`None`, a string
+            checkpoint identifier or an actual pre-trained model inheriting from
+            :class:`~transformers.PreTrainedModel` for PyTorch and :class:`~transformers.TFPreTrainedModel` for
+            TensorFlow.
+
+            If :obj:`None`, the default of the pipeline will be loaded.
+        tokenizer (:obj:`str` or :obj:`~transformers.PreTrainedTokenizer`, `optional`, defaults to :obj:`None`):
+            The tokenizer that will be used by the pipeline to encode data for the model. This can be :obj:`None`,
+            a string checkpoint identifier or an actual pre-trained tokenizer inheriting from
+            :class:`~transformers.PreTrainedTokenizer`.
+
+            If :obj:`None`, the default of the pipeline will be loaded.
+        modelcard (:obj:`str` or :class:`~transformers.ModelCard`, `optional`, defaults to :obj:`None`):
+            Model card attributed to the model for this pipeline.
+        framework (:obj:`str`, `optional`, defaults to :obj:`None`):
+            The framework to use, either "pt" for PyTorch or "tf" for TensorFlow. The specified framework must be
+            installed.
+
+            If no framework is specified, will default to the one currently installed. If no framework is specified
+            and both frameworks are installed, will default to PyTorch.
+        args_parser (:class:`~transformers.pipelines.ArgumentHandler`, `optional`, defaults to :obj:`None`):
+            Reference to the object in charge of parsing supplied pipeline parameters.
+        device (:obj:`int`, `optional`, defaults to :obj:`-1`):
+            Device ordinal for CPU/GPU supports. Setting this to -1 will leverage CPU, >=0 will run the model
+            on the associated CUDA device id.
     """
 
+    task = "sentiment-analysis"
+
     def __call__(self, *args, **kwargs):
         outputs = super().__call__(*args, **kwargs)
         scores = np.exp(outputs) / np.exp(outputs).sum(-1)
@@ -509,12 +623,53 @@ class TextClassificationPipeline(Pipeline):
 
 class FillMaskPipeline(Pipeline):
     """
-    Masked language modeling prediction pipeline using ModelWithLMHead head.
+    Masked language modeling prediction pipeline using ModelWithLMHead head. See the
+    `masked language modeling usage <../usage.html#masked-language-modeling>`__ examples for more information.
+
+    This mask filling pipeline can currently be loaded from the :func:`~transformers.pipeline` method using
+    the following task identifier(s):
+
+    - "fill-mask", for predicting masked tokens in a sequence.
+
+    The models that this pipeline can use are models that have been trained with a masked language modeling objective,
+    which includes the bi-directional models in the library.
+    See the list of available community models on
+    `huggingface.co/models <https://huggingface.co/models?search=&filter=lm-head>`__.
+
+    Arguments:
+        model (:obj:`str` or :obj:`~transformers.PreTrainedModel` or :obj:`~transformers.TFPreTrainedModel`, `optional`, defaults to :obj:`None`):
+            The model that will be used by the pipeline to make predictions. This can be :obj:`None`, a string
+            checkpoint identifier or an actual pre-trained model inheriting from
+            :class:`~transformers.PreTrainedModel` for PyTorch and :class:`~transformers.TFPreTrainedModel` for
+            TensorFlow.
+
+            If :obj:`None`, the default of the pipeline will be loaded.
+        tokenizer (:obj:`str` or :obj:`~transformers.PreTrainedTokenizer`, `optional`, defaults to :obj:`None`):
+            The tokenizer that will be used by the pipeline to encode data for the model. This can be :obj:`None`,
+            a string checkpoint identifier or an actual pre-trained tokenizer inheriting from
+            :class:`~transformers.PreTrainedTokenizer`.
+
+            If :obj:`None`, the default of the pipeline will be loaded.
+        modelcard (:obj:`str` or :class:`~transformers.ModelCard`, `optional`, defaults to :obj:`None`):
+            Model card attributed to the model for this pipeline.
+        framework (:obj:`str`, `optional`, defaults to :obj:`None`):
+            The framework to use, either "pt" for PyTorch or "tf" for TensorFlow. The specified framework must be
+            installed.
+
+            If no framework is specified, will default to the one currently installed. If no framework is specified
+            and both frameworks are installed, will default to PyTorch.
+        args_parser (:class:`~transformers.pipelines.ArgumentHandler`, `optional`, defaults to :obj:`None`):
+            Reference to the object in charge of parsing supplied pipeline parameters.
+        device (:obj:`int`, `optional`, defaults to :obj:`-1`):
+            Device ordinal for CPU/GPU supports. Setting this to -1 will leverage CPU, >=0 will run the model
+            on the associated CUDA device id.
     """
 
+    task = "fill-mask"
+
     def __init__(
         self,
-        model,
+        model: Optional = None,
         tokenizer: PreTrainedTokenizer = None,
         modelcard: Optional[ModelCard] = None,
         framework: Optional[str] = None,
@@ -574,14 +729,57 @@ class FillMaskPipeline(Pipeline):
 
 class NerPipeline(Pipeline):
     """
-    Named Entity Recognition pipeline using ModelForTokenClassification head.
+    Named Entity Recognition pipeline using ModelForTokenClassification head. See the
+    `named entity recognition usage <../usage.html#named-entity-recognition>`__ examples for more information.
+
+    This token recognition pipeline can currently be loaded from the :func:`~transformers.pipeline` method using
+    the following task identifier(s):
+
+    - "ner", for predicting the classes of tokens in a sequence: person, organisation, location or miscellaneous.
+
+    The models that this pipeline can use are models that have been fine-tuned on a token classification task.
+    See the list of available community models fine-tuned on such a task on
+    `huggingface.co/models <https://huggingface.co/models?search=&filter=token-classification>`__.
+
+    Arguments:
+        model (:obj:`str` or :obj:`~transformers.PreTrainedModel` or :obj:`~transformers.TFPreTrainedModel`, `optional`, defaults to :obj:`None`):
+            The model that will be used by the pipeline to make predictions. This can be :obj:`None`, a string
+            checkpoint identifier or an actual pre-trained model inheriting from
+            :class:`~transformers.PreTrainedModel` for PyTorch and :class:`~transformers.TFPreTrainedModel` for
+            TensorFlow.
+
+            If :obj:`None`, the default of the pipeline will be loaded.
+        tokenizer (:obj:`str` or :obj:`~transformers.PreTrainedTokenizer`, `optional`, defaults to :obj:`None`):
+            The tokenizer that will be used by the pipeline to encode data for the model. This can be :obj:`None`,
+            a string checkpoint identifier or an actual pre-trained tokenizer inheriting from
+            :class:`~transformers.PreTrainedTokenizer`.
+
+            If :obj:`None`, the default of the pipeline will be loaded.
+        modelcard (:obj:`str` or :class:`~transformers.ModelCard`, `optional`, defaults to :obj:`None`):
+            Model card attributed to the model for this pipeline.
+        framework (:obj:`str`, `optional`, defaults to :obj:`None`):
+            The framework to use, either "pt" for PyTorch or "tf" for TensorFlow. The specified framework must be
+            installed.
+
+            If no framework is specified, will default to the one currently installed. If no framework is specified
+            and both frameworks are installed, will default to PyTorch.
+        args_parser (:class:`~transformers.pipelines.ArgumentHandler`, `optional`, defaults to :obj:`None`):
+            Reference to the object in charge of parsing supplied pipeline parameters.
+        device (:obj:`int`, `optional`, defaults to :obj:`-1`):
+            Device ordinal for CPU/GPU supports. Setting this to -1 will leverage CPU, >=0 will run the model
+            on the associated CUDA device id.
+
+    Example::
+
+        from transformers import pi
     """
 
     default_input_names = "sequences"
+    task = "ner"
 
     def __init__(
         self,
-        model,
+        model: Optional = None,
         tokenizer: PreTrainedTokenizer = None,
         modelcard: Optional[ModelCard] = None,
         framework: Optional[str] = None,
@@ -716,15 +914,54 @@ class QuestionAnsweringArgumentHandler(ArgumentHandler):
 
 class QuestionAnsweringPipeline(Pipeline):
     """
-    Question Answering pipeline using ModelForQuestionAnswering head.
+    Question Answering pipeline using ModelForQuestionAnswering head. See the
+    `question answering usage <../usage.html#question-answering>`__ examples for more information.
+
+    This question answering can currently be loaded from the :func:`~transformers.pipeline` method using
+    the following task identifier(s):
+
+    - "question-answering", for answering questions given a context.
+
+    The models that this pipeline can use are models that have been fine-tuned on a question answering task.
+    See the list of available community models fine-tuned on such a task on
+    `huggingface.co/models <https://huggingface.co/models?search=&filter=question-answering>`__.
+
+    Arguments:
+        model (:obj:`str` or :obj:`~transformers.PreTrainedModel` or :obj:`~transformers.TFPreTrainedModel`, `optional`, defaults to :obj:`None`):
+            The model that will be used by the pipeline to make predictions. This can be :obj:`None`, a string
+            checkpoint identifier or an actual pre-trained model inheriting from
+            :class:`~transformers.PreTrainedModel` for PyTorch and :class:`~transformers.TFPreTrainedModel` for
+            TensorFlow.
+
+            If :obj:`None`, the default of the pipeline will be loaded.
+        tokenizer (:obj:`str` or :obj:`~transformers.PreTrainedTokenizer`, `optional`, defaults to :obj:`None`):
+            The tokenizer that will be used by the pipeline to encode data for the model. This can be :obj:`None`,
+            a string checkpoint identifier or an actual pre-trained tokenizer inheriting from
+            :class:`~transformers.PreTrainedTokenizer`.
+
+            If :obj:`None`, the default of the pipeline will be loaded.
+        modelcard (:obj:`str` or :class:`~transformers.ModelCard`, `optional`, defaults to :obj:`None`):
+            Model card attributed to the model for this pipeline.
+        framework (:obj:`str`, `optional`, defaults to :obj:`None`):
+            The framework to use, either "pt" for PyTorch or "tf" for TensorFlow. The specified framework must be
+            installed.
+
+            If no framework is specified, will default to the one currently installed. If no framework is specified
+            and both frameworks are installed, will default to PyTorch.
+        args_parser (:class:`~transformers.pipelines.ArgumentHandler`, `optional`, defaults to :obj:`None`):
+            Reference to the object in charge of parsing supplied pipeline parameters.
+        device (:obj:`int`, `optional`, defaults to :obj:`-1`):
+            Device ordinal for CPU/GPU supports. Setting this to -1 will leverage CPU, >=0 will run the model
+            on the associated CUDA device id.
     """
 
     default_input_names = "question,context"
+    task = "question-answering"
 
     def __init__(
         self,
-        model,
-        tokenizer: Optional[PreTrainedTokenizer],
+        model: Optional = None,
+        tokenizer: Optional[PreTrainedTokenizer] = None,
         modelcard: Optional[ModelCard] = None,
         framework: Optional[str] = None,
         device: int = -1,
@@ -1003,23 +1240,77 @@ def pipeline(
     model: Optional = None,
     config: Optional[Union[str, PretrainedConfig]] = None,
     tokenizer: Optional[Union[str, PreTrainedTokenizer]] = None,
-    modelcard: Optional[Union[str, ModelCard]] = None,
     framework: Optional[str] = None,
     **kwargs
 ) -> Pipeline:
     """
     Utility factory method to build a pipeline.
+
     Pipeline are made of:
-        A Tokenizer instance in charge of mapping raw textual input to token
-        A Model instance
-        Some (optional) post processing for enhancing model's output
 
-    Examples:
+        - A Tokenizer instance in charge of mapping raw textual input to token
+        - A Model instance
+        - Some (optional) post processing for enhancing model's output
+
+
+    Args:
+        task (:obj:`str`):
+            The task defining which pipeline will be returned. Currently accepted tasks are:
+
+            - "feature-extraction": will return a :class:`~transformers.FeatureExtractionPipeline`
+            - "sentiment-analysis": will return a :class:`~transformers.TextClassificationPipeline`
+            - "ner": will return a :class:`~transformers.NerPipeline`
+            - "question-answering": will return a :class:`~transformers.QuestionAnsweringPipeline`
+            - "fill-mask": will return a :class:`~transformers.FillMaskPipeline`
+        model (:obj:`str` or :obj:`~transformers.PreTrainedModel` or :obj:`~transformers.TFPreTrainedModel`, `optional`, defaults to :obj:`None`):
+            The model that will be used by the pipeline to make predictions. This can be :obj:`None`, a string
+            checkpoint identifier or an actual pre-trained model inheriting from
+            :class:`~transformers.PreTrainedModel` for PyTorch and :class:`~transformers.TFPreTrainedModel` for
+            TensorFlow.
+
+            If :obj:`None`, the default of the pipeline will be loaded.
+        config (:obj:`str` or :obj:`~transformers.PretrainedConfig`, `optional`, defaults to :obj:`None`):
+            The configuration that will be used by the pipeline to instantiate the model. This can be :obj:`None`,
+            a string checkpoint identifier or an actual pre-trained model configuration inheriting from
+            :class:`~transformers.PretrainedConfig`.
+
+            If :obj:`None`, the default of the pipeline will be loaded.
+        tokenizer (:obj:`str` or :obj:`~transformers.PreTrainedTokenizer`, `optional`, defaults to :obj:`None`):
+            The tokenizer that will be used by the pipeline to encode data for the model. This can be :obj:`None`,
+            a string checkpoint identifier or an actual pre-trained tokenizer inheriting from
+            :class:`~transformers.PreTrainedTokenizer`.
+
+            If :obj:`None`, the default of the pipeline will be loaded.
+        framework (:obj:`str`, `optional`, defaults to :obj:`None`):
+            The framework to use, either "pt" for PyTorch or "tf" for TensorFlow. The specified framework must be
+            installed.
+
+            If no framework is specified, will default to the one currently installed. If no framework is specified
+            and both frameworks are installed, will default to PyTorch.
+
+    Returns:
+        :class:`~transformers.Pipeline`: Class inheriting from :class:`~transformers.Pipeline`, according to
+        the task.
+
+    Examples::
+
+        from transformers import pipeline, AutoModelForTokenClassification, AutoTokenizer
+
+        # Sentiment analysis pipeline
         pipeline('sentiment-analysis')
+
+        # Question answering pipeline, specifying the checkpoint identifier
         pipeline('question-answering', model='distilbert-base-cased-distilled-squad', tokenizer='bert-base-cased')
-        pipeline('ner', model=AutoModel.from_pretrained(...), tokenizer=AutoTokenizer.from_pretrained(...)
-        pipeline('ner', model='dbmdz/bert-large-cased-finetuned-conll03-english', tokenizer='bert-base-cased')
-        pipeline('ner', model='https://...pytorch-model.bin', config='https://...config.json', tokenizer='bert-base-cased')
+
+        # Named entity recognition pipeline, passing in a specific model and tokenizer
+        model = AutoModelForTokenClassification.from_pretrained("dbmdz/bert-large-cased-finetuned-conll03-english")
+        tokenizer = AutoTokenizer.from_pretrained("bert-base-cased")
+        pipeline('ner', model=model, tokenizer=tokenizer)
+
+        # Named entity recognition pipeline, passing a model and configuration with a HTTPS URL.
+        model_url = "https://s3.amazonaws.com/models.huggingface.co/bert/dbmdz/bert-large-cased-finetuned-conll03-english/pytorch_model.bin"
+        config_url = "https://s3.amazonaws.com/models.huggingface.co/bert/dbmdz/bert-large-cased-finetuned-conll03-english/config.json"
+        pipeline('ner', model=model_url, config=config_url, tokenizer='bert-base-cased')
     """
     # Retrieve the task
     if task not in SUPPORTED_TASKS:
@@ -1048,13 +1339,12 @@ def pipeline(
                 "Please provided a PretrainedTokenizer class or a path/url/shortcut name to a pretrained tokenizer."
             )
 
+    modelcard = None
     # Try to infer modelcard from model or config name (if provided as str)
-    if modelcard is None:
-        # Try to fallback on one of the provided string for model or config (will replace the suffix)
-        if isinstance(model, str):
-            modelcard = model
-        elif isinstance(config, str):
-            modelcard = config
+    if isinstance(model, str):
+        modelcard = model
+    elif isinstance(config, str):
+        modelcard = config
 
     # Instantiate tokenizer if needed
     if isinstance(tokenizer, (str, tuple)):

tests/test_pipelines.py

@@ -2,9 +2,16 @@ import unittest
 from typing import Iterable, List, Optional
 
 from transformers import pipeline
-from transformers.pipelines import Pipeline
+from transformers.pipelines import (
+    FeatureExtractionPipeline,
+    FillMaskPipeline,
+    NerPipeline,
+    Pipeline,
+    QuestionAnsweringPipeline,
+    TextClassificationPipeline,
+)
 
-from .utils import require_tf, require_torch
+from .utils import require_tf, require_torch, slow
 
 
 QA_FINETUNED_MODELS = [
@@ -304,3 +311,30 @@ class MultiColumnInputTestCase(unittest.TestCase):
         for tokenizer, model, config in TF_QA_FINETUNED_MODELS:
             nlp = pipeline(task="question-answering", model=model, config=config, tokenizer=tokenizer, framework="tf")
             self._test_multicolumn_pipeline(nlp, valid_samples, invalid_samples, mandatory_output_keys)
+
+
+class PipelineCommonTests(unittest.TestCase):
+
+    pipelines = (
+        NerPipeline,
+        FeatureExtractionPipeline,
+        QuestionAnsweringPipeline,
+        FillMaskPipeline,
+        TextClassificationPipeline,
+    )
+
+    @slow
+    @require_tf
+    def test_tf_defaults(self):
+        # Test that pipelines can be correctly loaded without any argument
+        for default_pipeline in self.pipelines:
+            with self.subTest(msg="Testing Torch defaults with PyTorch and {}".format(default_pipeline.task)):
+                default_pipeline(framework="tf")
+
+    @slow
+    @require_torch
+    def test_pt_defaults(self):
+        # Test that pipelines can be correctly loaded without any argument
+        for default_pipeline in self.pipelines:
+            with self.subTest(msg="Testing Torch defaults with PyTorch and {}".format(default_pipeline.task)):
+                default_pipeline(framework="pt")