GitLab

* AdaFactor optimizer ported from fairseq. Tested for T5 finetuning and MLM -- reduced memory consumption compared to ADAM.

* update PR fixes, add basic test

* bug -- incorrect params in test

* bugfix -- import Adafactor into test

* bugfix -- removed accidental T5 include

* resetting T5 to master

* bugfix -- include Adafactor in __init__

* longer loop for adafactor test

* remove double error class declare

* lint

* black

* isort

* Update src/transformers/optimization.py
Co-authored-by: Sam Shleifer <sshleifer@gmail.com>

* single docstring

* Cleanup docstring
Co-authored-by: Nikolai Y <nikolai.yakovenko@point72.com>
Co-authored-by: Sam Shleifer <sshleifer@gmail.com>