[DOC] documentation is not clear and implied that PyT Trainer class cannot support BC and Regression

[rnyak]

We need to clarify in the documentation that PyT Trainer class cannot support BC and Regression. We should explain what users can use for these tasks instead of Trainer Class : they can use custom developed model.fit() and model.evaluate().

[rnyak]

@sararb with the new PRs do we add any explanation in the docs?

[sararb]

Yes, It is planned to add the documentation about how to train BC/regression with the HF Trainer class after the task #554 is finalized.