add type annotations to torch.nn.modules.container (#48969)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/48968
Pull Request resolved: https://github.com/pytorch/pytorch/pull/48969
Reviewed By: mrshenli
Differential Revision: D25728987
Pulled By: walterddr
fbshipit-source-id: 02c3aa2078f4ed6cc6edd90ffe1177d789c328a9
