Add ESM to hugging face
Author: liujas000
Pull request: yes

# What does this PR do?

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Fixes # (issue)


## Before submitting
- [ ] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
- [ ] Did you read the [contributor guideline](https://github.com/huggingface/transformers/blob/master/CONTRIBUTING.md#start-contributing-pull-requests),
      Pull Request section?
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      [documentation guidelines](https://github.com/huggingface/transformers/tree/master/docs), and
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- [ ] Did you write any new necessary tests?


## Who can review?

Anyone in the community is free to review the PR once the tests have passed. Feel free to tag
members/contributors who may be interested in your PR.

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Models:

- albert, bert, xlm: @LysandreJik
- blenderbot, bart, marian, pegasus, encoderdecoder,  t5: @patrickvonplaten, @patil-suraj
- longformer, reformer, transfoxl, xlnet: @patrickvonplaten
- fsmt: @stas00
- funnel: @sgugger
- gpt2: @patrickvonplaten, @LysandreJik
- rag: @patrickvonplaten, @lhoestq
- tensorflow: @LysandreJik

Library:

- benchmarks: @patrickvonplaten
- deepspeed: @stas00
- ray/raytune: @richardliaw, @amogkam
- text generation: @patrickvonplaten
- tokenizers: @n1t0, @LysandreJik
- trainer: @sgugger
- pipelines: @LysandreJik

Documentation: @sgugger

HF projects:

- datasets: [different repo](https://github.com/huggingface/datasets)
- rust tokenizers: [different repo](https://github.com/huggingface/tokenizers)

Examples:

- maintained examples (not research project or legacy): @sgugger, @patil-suraj
- research_projects/bert-loses-patience: @JetRunner
- research_projects/distillation: @VictorSanh

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Comments:
Thanks for showing us the diff @Jason Liu! Those are the kind of changes we usually try to avoid: the core philosophy of the Transformers library is to have individual model files that only contain the code related to their model and not building blocks with lots of config parameters. For instance mBART, marian and BART are all pretty similar, yet there all have their own modeling files. RoBERTa is not that different from BERT, yet we also chose to have two different config/modeling files. Also, moving the LayerNorm module is breaking and will make every roberta checkpoint on the model hub fail, which is something no one really wants :-)

This is something that our users have said they really like about the library so we want to continue like this! That being said, to ensure the duplicate parts of the code don't diverge, we have internal scripts. You may have seen some # Copied from xxx statements in the roberta modeling file for instance, they are all there to enforce the copies stay synced with the originals.
So having a new esm model with the # Copied from xxx statements where necessary is the solution we would really like to see. Let us know how we can help you along the way! There is a template to add new models [here](https://github.com/huggingface/transformers/tree/master/templates/adding_a_new_model). If you follow the README, it will do all the steps to fully integrate a new model in the library that passes all the tests, you will just have to change the modeling file afterward with what you've shown us in the PR.

This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

Please note that issues that do not follow the [contributing guidelines](https://github.com/huggingface/transformers/blob/master/CONTRIBUTING.md) are likely to be ignored.