GitLab

* Adding support for multiple mask tokens.

- Original implem: https://github.com/huggingface/transformers/pull/10222

Co-authored-by: njafer <naveen.jafer@oracle.com>

* In order to accomodate optionally multimodal models like Perceiver

we add information to the tasks to specify tasks where we know for sure
if we need the tokenizer/feature_extractor or not.

* Adding info in the documentation about multi masks.

+ marked as experimental.

* Add a copy() to prevent overriding the same tensor over and over.

* Fixup.

* Adding small test for multi mask with real values..
Co-authored-by: njafer <naveen.jafer@oracle.com>