Add type hint for SequentialSampler (#56374)
Summary:
Add type hint for SequentialSampler
Pull Request resolved: https://github.com/pytorch/pytorch/pull/56374
Reviewed By: heitorschueroff
Differential Revision: D27884528
Pulled By: ejguan
fbshipit-source-id: 68eb900643098565743245c843e76e464f981458
