add type annotations to common_nn.py (#48190)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/48189
Pull Request resolved: https://github.com/pytorch/pytorch/pull/48190
Reviewed By: walterddr, zhangguanheng66
Differential Revision: D25245261
Pulled By: malfet
fbshipit-source-id: 0eabaed54996be83ead0fd7668f4d2be20adfc17
