[WIP] Add BROS
# What does this PR do?

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Add [BROS(BERT Relying On Spatiality)](https://arxiv.org/abs/2108.04539) to 🤗 Transformers


## Before submitting
- [ ] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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      Pull Request section?
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      to it if that's the case.
- [ ] Did you make sure to update the documentation with your changes? Here are the
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- [ ] Did you write any new necessary tests?


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@NielsRogge 
@jinhopark8345 Awesome work - looking forward to having this model added! Feel free to ping us when the PR is ready for review or you have any implementation questions in the meantime. <|||||>@amyeroberts 

I am confused about what needs to be done.

According to the [How to add a new model](https://huggingface.co/docs/transformers/add_new_model#514-port-brandnewbert-to-transformers) guideline, a big part of it is porting pretrained models (from the original repo) into Huggingface transformers and making sure they are correctly ported by checking the outputs of each layer's forward step.

However, it seems like the authors of the Bros model used `transformers-cli` to create the boilerplate code, and I don't think there is much to change from the [original code](https://github.com/clovaai/bros/blob/master/bros/modeling_bros.py).

Do I need to write a conversion script? Or can I skip this step and move to the step where I add model test codes?

Thanks for the help in advance!<|||||>@jinhopark8345  Interesting - that will definitely make things easier! In this case, if the files are already on the hub and in the correct format, there's no need for the conversion script. It's possible there might be additional arguments required in the config files or additional files needed in the hub repo, in which case, I'd suggest writing a script to add these. You probably won't be able to write directly to the org's repo, but can open a PR with any necessary changes. <|||||>The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_23190). All of your documentation changes will be reflected on that endpoint.<|||||>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/main/CONTRIBUTING.md) are likely to be ignored.<|||||>Still working on it! Writing tutorial/demo notebooks of how to use BROS <|||||>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/main/CONTRIBUTING.md) are likely to be ignored.<|||||>@amyeroberts Is it possible to reopen this PR because I have been working on [forked repo](https://github.com/jinhopark8345/bros/tree/feature/update-data-loading)  of original bros code