GitLab

* Add {decoder_,}head_mask to LED

* Fix create_custom_forward signatue in encoder

* Add head_mask to longformer

* Add head_mask to longformer to fix dependencies
of LED on Longformer.

* Not working yet

* Add mising one input in longofrmer_modeling.py

* make fix-copies

* fix common inputs pt flakey led

* fix other tests correspondingly

* fix generation models

* fix led

* fix docs

* add is_decoder

* fix last docstrings

* make style

* fix t5 cross attentions

* correct t5

* create model

* add integration

* save current state

* make integration tests pass

* add one more test

* add explanation to tests

* remove from bart

* add padding

* remove unnecessary test

* make all tests pass

* re-add cookie cutter tests

* finish PyTorch

* fix attention test

* Update tests/test_modeling_common.py

* revert change

* remove unused file

* add string to doc

* save intermediate

* make tf integration tests pass

* finish tf

* fix doc

* fix docs again

* add led to doctree

* add to auto tokenizer

* added tips for led

* make style

* apply jplus statements

* correct tf longformer

* apply lysandres suggestions

* apply sylvains suggestions

* Apply suggestions from code review