Added documentation for data collator. (#10941)

* Added documentation for data collator.

* Update docs/source/data_collator.rst
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

* Added documentation for data collator.

* Added documentation for the data collator.

* Merge branch 'doc_DataCollator' of C:\Users\mahii\PycharmProjects\transformers with conflicts.

* Update documentation for the data collator.

* Update documentation for the data collator.
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>
Co-authored-by: Amna <A.A.Ahmad@student.tudelft.nl>

docs/source/index.rst

@@ -415,6 +415,7 @@ TensorFlow and/or Flax.
 
     main_classes/callback
     main_classes/configuration
+    main_classes/data_collator
     main_classes/logging
     main_classes/model
     main_classes/optimizer_schedules

docs/source/main_classes/data_collator.rst

+<!--- Copyright 2020 The 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.
+
+-->
+
+DataCollator
+-----------------------------------------------------------------------------------------------------------------------
+
+DataCollators are objects that will form a batch by using a list of elements as input. These lists of elements are of
+the same type as the elements of :obj:`train_dataset` or :obj:`eval_dataset`.
+
+A data collator will default to :func:`transformers.data.data_collator.default_data_collator` if no `tokenizer` has
+been provided. This is a function that takes a list of samples from a Dataset as input and collates them into a batch
+of a dict-like object. The default collator performs special handling of potential keys:
+
+    - ``label``: handles a single value (int or float) per object
+    - ``label_ids``: handles a list of values per object
+
+This function does not perform any preprocessing. An example of use can be found in glue and ner.
+
+
+Default data collator
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. autofunction:: transformers.data.data_collator.default_data_collator
+
+
+DataCollatorWithPadding
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. autoclass:: transformers.data.data_collator.DataCollatorWithPadding
+    :special-members: __call__
+    :members:
+
+DataCollatorForTokenClassification
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. autoclass:: transformers.data.data_collator.DataCollatorForTokenClassification
+    :special-members: __call__
+    :members:
+
+DataCollatorForSeq2Seq
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. autoclass:: transformers.data.data_collator.DataCollatorForSeq2Seq
+    :special-members: __call__
+    :members:
+
+DataCollatorForLanguageModeling
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. autoclass:: transformers.data.data_collator.DataCollatorForLanguageModeling
+    :special-members: __call__
+    :members: mask_tokens
+
+DataCollatorForWholeWordMask
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. autoclass:: transformers.data.data_collator.DataCollatorForWholeWordMask
+    :special-members: __call__
+    :members: mask_tokens
+
+DataCollatorForSOP
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. autoclass:: transformers.data.data_collator.DataCollatorForSOP
+    :special-members: __call__
+    :members: mask_tokens
+
+DataCollatorForPermutationLanguageModeling
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. autoclass:: transformers.data.data_collator.DataCollatorForPermutationLanguageModeling
+    :special-members: __call__
+    :members: mask_tokens