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docs/source/en/model_doc/bart.mdx

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+<!--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
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+http://www.apache.org/licenses/LICENSE-2.0
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+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.
+-->
+
+# BART
+
+**DISCLAIMER:** If you see something strange, file a [Github Issue](https://github.com/huggingface/transformers/issues/new?assignees=&labels=&template=bug-report.md&title) and assign
+@patrickvonplaten
+
+## Overview
+
+The Bart model was proposed in [BART: Denoising Sequence-to-Sequence Pre-training for Natural Language Generation,
+Translation, and Comprehension](https://arxiv.org/abs/1910.13461) by Mike Lewis, Yinhan Liu, Naman Goyal, Marjan
+Ghazvininejad, Abdelrahman Mohamed, Omer Levy, Ves Stoyanov and Luke Zettlemoyer on 29 Oct, 2019.
+
+According to the abstract,
+
+- Bart uses a standard seq2seq/machine translation architecture with a bidirectional encoder (like BERT) and a
+  left-to-right decoder (like GPT).
+- The pretraining task involves randomly shuffling the order of the original sentences and a novel in-filling scheme,
+  where spans of text are replaced with a single mask token.
+- BART is particularly effective when fine tuned for text generation but also works well for comprehension tasks. It
+  matches the performance of RoBERTa with comparable training resources on GLUE and SQuAD, achieves new
+  state-of-the-art results on a range of abstractive dialogue, question answering, and summarization tasks, with gains
+  of up to 6 ROUGE.
+
+This model was contributed by [sshleifer](https://huggingface.co/sshleifer). The Authors' code can be found [here](https://github.com/pytorch/fairseq/tree/master/examples/bart).
+
+
+### Examples
+
+- Examples and scripts for fine-tuning BART and other models for sequence to sequence tasks can be found in
+  [examples/pytorch/summarization/](https://github.com/huggingface/transformers/tree/main/examples/pytorch/summarization/README.md).
+- An example of how to train [`BartForConditionalGeneration`] with a Hugging Face `datasets`
+  object can be found in this [forum discussion](https://discuss.huggingface.co/t/train-bart-for-conditional-generation-e-g-summarization/1904).
+- [Distilled checkpoints](https://huggingface.co/models?search=distilbart) are described in this [paper](https://arxiv.org/abs/2010.13002).
+
+
+## Implementation Notes
+
+- Bart doesn't use `token_type_ids` for sequence classification. Use [`BartTokenizer`] or
+  [`~BartTokenizer.encode`] to get the proper splitting.
+- The forward pass of [`BartModel`] will create the `decoder_input_ids` if they are not passed.
+  This is different than some other modeling APIs. A typical use case of this feature is mask filling.
+- Model predictions are intended to be identical to the original implementation when
+  `forced_bos_token_id=0`. This only works, however, if the string you pass to
+  [`fairseq.encode`] starts with a space.
+- [`~generation_utils.GenerationMixin.generate`] should be used for conditional generation tasks like
+  summarization, see the example in that docstrings.
+- Models that load the *facebook/bart-large-cnn* weights will not have a `mask_token_id`, or be able to perform
+  mask-filling tasks.
+
+## Mask Filling
+
+The `facebook/bart-base` and `facebook/bart-large` checkpoints can be used to fill multi-token masks.
+
+```python
+from transformers import BartForConditionalGeneration, BartTokenizer
+
+model = BartForConditionalGeneration.from_pretrained("facebook/bart-large", forced_bos_token_id=0)
+tok = BartTokenizer.from_pretrained("facebook/bart-large")
+example_english_phrase = "UN Chief Says There Is No <mask> in Syria"
+batch = tok(example_english_phrase, return_tensors="pt")
+generated_ids = model.generate(batch["input_ids"])
+assert tok.batch_decode(generated_ids, skip_special_tokens=True) == [
+    "UN Chief Says There Is No Plan to Stop Chemical Weapons in Syria"
+]
+```
+
+## BartConfig
+
+[[autodoc]] BartConfig
+    - all
+
+## BartTokenizer
+
+[[autodoc]] BartTokenizer
+    - all
+
+## BartTokenizerFast
+
+[[autodoc]] BartTokenizerFast
+    - all
+
+## BartModel
+
+[[autodoc]] BartModel
+    - forward
+
+## BartForConditionalGeneration
+
+[[autodoc]] BartForConditionalGeneration
+    - forward
+
+## BartForSequenceClassification
+
+[[autodoc]] BartForSequenceClassification
+    - forward
+
+## BartForQuestionAnswering
+
+[[autodoc]] BartForQuestionAnswering
+    - forward
+
+## BartForCausalLM
+
+[[autodoc]] BartForCausalLM
+    - forward
+
+## TFBartModel
+
+[[autodoc]] TFBartModel
+    - call
+
+## TFBartForConditionalGeneration
+
+[[autodoc]] TFBartForConditionalGeneration
+    - call
+
+## FlaxBartModel
+
+[[autodoc]] FlaxBartModel
+    - __call__
+    - encode
+    - decode
+
+## FlaxBartForConditionalGeneration
+
+[[autodoc]] FlaxBartForConditionalGeneration
+    - __call__
+    - encode
+    - decode
+
+## FlaxBartForSequenceClassification
+
+[[autodoc]] FlaxBartForSequenceClassification
+    - __call__
+    - encode
+    - decode
+
+## FlaxBartForQuestionAnswering
+
+[[autodoc]] FlaxBartForQuestionAnswering
+    - __call__
+    - encode
+    - decode
+
+## FlaxBartForCausalLM
+
+[[autodoc]] FlaxBartForCausalLM
+    - __call__