convert pytorch checkpoints to TF1.x checkpoints (reverse of transformers-cli convert)
# 🚀 Feature request

Hello, 
Some BERT models were pre-trained using Huggingface/Facebook/NIVIDA's implementations and only have `pytorch.bin`. I am wondering if I can convert the checkpoints to  TF1.x (compatible with google's BERT https://github.com/google-research/bert).



Hello! We don't have a conversion script capable of doing that. Is there a feature of google-research/bert we could implement to make your life easier with `transformers` ?<|||||>This is simply for comparison reasons. We want to see if there is a performance difference due to the implementation. 

By the way, I also tried to convert the PyTorch checkpoint to TF2 using the `convert_pytorch_checkpoint_to_tf2.py` script. But I got this error:

```
$ python convert_pytorch_checkpoint_to_tf2.py 
Traceback (most recent call last):
  File "convert_pytorch_checkpoint_to_tf2.py", line 21, in <module>
    from . import (
ImportError: attempted relative import with no known parent package
```

I am using transformers v4.10.0 and I have installed this package. 

Thanks! 
Li
<|||||>By the way, my python version is 3.8.11
I am using ubuntu 18.04<|||||>> Is there a feature of google-research/bert we could implement to make your life easier with transformers? 

the `run_classifier.py` script supports input of tsv text. the `datasets` library of huggingface only supports csv format. tsv format is easier to parse than csv format. <|||||>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.