Repository: transformers
Issue: [Community Event] Doc Tests Sprint
Labels: Good First Issue

### This issue is part of our **Doc Test Sprint**. If you're interested in helping out come [join us on Discord](https://discord.gg/J8bW9u5abB) and talk with other contributors!

Docstring examples are often the first point of contact when trying out a new library! So far we haven't done a very good job at ensuring that all docstring examples work correctly in 🤗 Transformers - but we're now very dedicated to ensure that all documentation examples work correctly by testing each documentation example via Python's doctest (https://docs.python.org/3/library/doctest.html) on a daily basis.

In short we should do the following for all models for both PyTorch and Tensorflow:
1. - Check the current doc examples will run without failure
2. - Check whether the current doc example of the forward method is a sensible example to better understand the model or whether it can be improved. E.g. is the example of https://huggingface.co/docs/transformers/v4.17.0/en/model_doc/bert#transformers.BertForQuestionAnswering.forward a good example of the model? Could it be improved?
3. -  Add an expected output to the doc example and test it via Python's doc test (see **Guide to contributing** below)

Adding a documentation test for a model is a great way to better understand how the model works, a simple (possibly first) contribution to Transformers and most importantly a very important contribution to the Transformers community 🔥 

If you're interested in adding a documentation test, please read through the **Guide to contributing** below.

This issue is a call for contributors, to make sure docstring exmaples of existing model architectures work correctly. If you wish to contribute, reply in this thread which architectures you'd like to take :)

### Guide to contributing:
1. Ensure you've read our contributing [guidelines](https://github.com/huggingface/transformers/blob/master/CONTRIBUTING.md) 📜 
2. Claim your architecture(s) in this thread (confirm no one is working on it) 🎯 
3. Implement the changes as in https://github.com/huggingface/transformers/pull/15987 (see the diff on the model architectures for a few examples) 💪 
    - The file you want to look at is in `src/transformers/models/[model_name]/modeling_[model_name].py`, `src/transformers/models/[model_name]/modeling_tf_[model_name].py` or `src/transformers/doc_utils.py` or `src/transformes/file_utils.py`
    - Make sure to run the doc example doc test locally as described in https://github.com/huggingface/transformers/tree/master/docs#for-python-files
    - Optionally, change the example docstring to a more sensible example that gives a better suited result
    - Make the test pass
    - Add the file name to https://github.com/huggingface/transformers/blob/master/utils/documentation_tests.txt (making sure the file stays in alphabetical order)
    - Run the doc example test again locally

    In addition, there are a few things we can also improve, for example : 
    - Fix some style issues: for example, change **``decoder_input_ids```** to **\`decoder_input_ids\`**.
    - Using a small model checkpoint instead of a large one: for example, change **"facebook/bart-large"** to **"facebook/bart-base"** (and adjust the expected outputs if any)
4. Open the PR and tag me @patrickvonplaten @ydshieh or @patil-suraj (don't forget to run `make fixup` before your final commit) 🎊 
    - Note that some code is copied across our codebase. If you see a line like `# Copied from transformers.models.bert...`, this means that the code is copied from that source, and our scripts will automatically keep that in sync. If you see that, you should not edit the copied method! Instead, edit the original method it's copied from, and run make fixup to synchronize that across all the copies. Be sure you installed the development dependencies with `pip install -e ".[dev]"`, as described in the contributor guidelines above, to ensure that the code quality tools in `make fixup` can run.

### PyTorch Model Examples added to tests:
- [ ] **ALBERT** (@vumichien)
- [x] **BART** (@abdouaziz)
- [x] BEiT
- [ ] **BERT** (@vumichien)
- [ ] Bert
- [ ] BigBird (@vumichien)
- [x] BigBirdPegasus
- [x] Blenderbot
- [x] BlenderbotSmall
- [ ] CamemBERT  (@abdouaziz)
- [ ] Canine (@NielsRogge)
- [ ] **CLIP** (@Aanisha)
- [ ] ConvBERT (@simonzli)
- [x] ConvNext
- [ ] CTRL (@jeremyadamsfisher)
- [x] Data2VecAudio
- [ ] Data2VecText
- [ ] DeBERTa (@Tegzes)
- [ ] **DeBERTa-v2** (@Tegzes)
- [x] DeiT
- [ ] DETR
- [ ] **DistilBERT** (@jmwoloso)
- [ ] DPR
- [ ] **ELECTRA** (@bhadreshpsavani)
- [ ] Encoder
- [ ] FairSeq
- [ ] FlauBERT (@abdouaziz)
- [ ] FNet
- [ ] Funnel
- [ ] **GPT2** (@ArEnSc)
- [ ] GPT-J (@ArEnSc)
- [x] Hubert
- [ ] I-BERT (@abdouaziz)
- [ ] ImageGPT
- [ ] LayoutLM (chiefchiefling @ discord)
- [ ] LayoutLMv2
- [ ] LED
- [x] **Longformer** (@KMFODA)
- [ ] LUKE (@Tegzes)
- [ ] LXMERT
- [ ] M2M100
- [x] **Marian**
- [x] MaskFormer (@reichenbch)
- [x] **mBART**
- [ ] MegatronBert
- [ ] MobileBERT (@vumichien)
- [ ] MPNet
- [ ] mT5
- [ ] Nystromformer
- [ ] OpenAI
- [ ] OpenAI
- [x] Pegasus
- [ ] Perceiver
- [x] PLBart
- [x] PoolFormer
- [ ] ProphetNet
- [ ] QDQBert
- [ ] RAG
- [ ] Realm
- [ ] **Reformer**
- [x] ResNet
- [ ] RemBERT
- [ ] RetriBERT
- [ ] **RoBERTa** (@patrickvonplaten )
- [ ] RoFormer
- [x] SegFormer
- [x] SEW
- [x] SEW-D
- [x] SpeechEncoderDecoder
- [x] Speech2Text
- [x] Speech2Text2
- [ ] Splinter
- [ ] SqueezeBERT
- [x] Swin
- [ ] **T5** (@MarkusSagen)
- [ ] TAPAS (@NielsRogge)
- [ ] Transformer-XL (@simonzli)
- [ ] TrOCR (@arnaudstiegler)
- [x] UniSpeech
- [x] UniSpeechSat
- [x] Van
- [x] ViLT
- [x] VisionEncoderDecoder
- [ ] VisionTextDualEncoder
- [ ] VisualBert
- [x] **ViT**
- [x] ViTMAE
- [x] **Wav2Vec2**
- [x] WavLM
- [ ] XGLM
- [ ] **XLM**
- [ ] **XLM-RoBERTa** (@AbinayaM02)
- [ ] XLM-RoBERTa-XL
- [ ] XLMProphetNet
- [ ] **XLNet**
- [ ] YOSO


### Tensorflow Model Examples added to tests:
- [ ] **ALBERT** (@vumichien)
- [ ] **BART**
- [ ] BEiT
- [ ] **BERT** (@vumichien)
- [ ] Bert
- [ ] BigBird (@vumichien)
- [ ] BigBirdPegasus
- [ ] Blenderbot
- [ ] BlenderbotSmall
- [ ] CamemBERT
- [ ] Canine
- [ ] **CLIP** (@Aanisha)
- [ ] ConvBERT (@simonzli)
- [ ] ConvNext
- [ ] CTRL
- [ ] Data2VecAudio
- [ ] Data2VecText
- [ ] DeBERTa
- [ ] **DeBERTa-v2**
- [ ] DeiT
- [ ] DETR
- [ ] **DistilBERT** (@jmwoloso)
- [ ] DPR
- [ ] **ELECTRA** (@bhadreshpsavani)
- [ ] Encoder
- [ ] FairSeq
- [ ] FlauBERT
- [ ] FNet
- [ ] Funnel
- [ ] **GPT2** (@cakiki)
- [ ] GPT-J (@cakiki)
- [ ] Hubert
- [ ] I-BERT
- [ ] ImageGPT
- [ ] LayoutLM
- [ ] LayoutLMv2
- [ ] LED
- [x] **Longformer** (@KMFODA)
- [ ] LUKE
- [ ] LXMERT
- [ ] M2M100
- [ ] **Marian**
- [x] MaskFormer (@reichenbch)
- [ ] **mBART**
- [ ] MegatronBert
- [ ] MobileBERT (@vumichien)
- [ ] MPNet
- [ ] mT5
- [ ] Nystromformer
- [ ] OpenAI
- [ ] OpenAI
- [ ] Pegasus
- [ ] Perceiver
- [ ] PLBart
- [ ] PoolFormer
- [ ] ProphetNet
- [ ] QDQBert
- [ ] RAG
- [ ] Realm
- [ ] **Reformer**
- [ ] ResNet
- [ ] RemBERT
- [ ] RetriBERT
- [ ] **RoBERTa** (@patrickvonplaten)
- [ ] RoFormer
- [ ] SegFormer
- [ ] SEW
- [ ] SEW-D
- [ ] SpeechEncoderDecoder
- [ ] Speech2Text
- [ ] Speech2Text2
- [ ] Splinter
- [ ] SqueezeBERT
- [ ] Swin (@johko)
- [ ] **T5** (@MarkusSagen)
- [ ] TAPAS
- [ ] Transformer-XL (@simonzli)
- [ ] TrOCR (@arnaudstiegler)
- [ ] UniSpeech
- [ ] UniSpeechSat
- [ ] Van
- [ ] ViLT
- [ ] VisionEncoderDecoder
- [ ] VisionTextDualEncoder
- [ ] VisualBert
- [ ] **ViT** (@johko)
- [ ] ViTMAE
- [ ] **Wav2Vec2**
- [ ] WavLM
- [ ] XGLM
- [ ] **XLM**
- [ ] **XLM-RoBERTa** (@AbinayaM02)
- [ ] XLM-RoBERTa-XL
- [ ] XLMProphetNet
- [ ] **XLNet**
- [ ] YOSO