tokenization_bart.py: return_tensors default should be "pt"
return_tensors default should be "pt" in bart's `prepare_seq2seq_batch`.
Tokenizers are supposed to be framework (PyTorch/TensorFlow/FLAX) agnostic so we probably don't want to do in that direction.<|||||>Gotcha. Is this going to be the case for all tokenizers in the future? Because currently they default to PyTorch except for Bart's.
Also, I think the docstring for Bart tokenizer's `return_tensors` needs to be updated then since it says: `optional`, defaults to "pt"<|||||>The fact that the BART-like tokenizers have `return_tensors="pt"` is a mistake. The tokenizers should be framework-agnostic.<|||||>We will have to update this, which will be a breaking change, so we'll try to put it in the v4.0.0. Do you want to open a PR to fix the issue?<|||||>Sure. I'll close this then and make a new PR for that.
<|||||>Hi @Mehrad0711! We're rushing to `transformers@v4.0.0`, and we don't want that in this release. I've taken the liberty of fixing it in https://github.com/huggingface/transformers/pull/8599. Sorry about that, I hope you had not started your development.

If you have, you can push your fixes and open a PR and I'll incorporate those changes in my PR and mark you as co-author.<|||||>No problem @LysandreJik . Thanks for fixing it!