Adding `optimizer` attribute to SequentialLR (#67406)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/67318 :)
cc albanD, datumbox
Pull Request resolved: https://github.com/pytorch/pytorch/pull/67406
Reviewed By: jbschlosser
Differential Revision: D31997873
Pulled By: albanD
fbshipit-source-id: f579fb886d049a545673fd92ef5892fcf501bcc6
