Add BioGPT
Author: kamalkraj
Pull request: yes

# What does this PR do?

Adding BioGPT

Original Implementation and weights - https://github.com/microsoft/BioGPT

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Fixes # (issue)


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Models:

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Comments:
_The documentation is not available anymore as the PR was closed or merged._

@younesbelkada 
Done changes according to your suggestions.
Thanks for the review

Thanks @kamalkraj 
Let me give it another round of review and I'll get back to you

@sgugger 
Done changes according to your suggestions.
Thanks for the review

Hi @kamalkraj 
The repo has been moved to microsoft: https://huggingface.co/microsoft/biogpt 
Could you please update the PR accordingly? Also it seems that you need to rebase to main
Thanks!

@younesbelkada Done the changes 
Thanks

thanks @kamalkraj !
It seems that styling tests are failing, could you please run `make fixup`?

@younesbelkada fixed

Thanks so much @kamalkraj !
Let's leave it now to @sgugger to give his review ;) 
Thanks!