Namespace isolation for classes (#19903)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/19903
ghimport-source-id: deadf59f469ad620d0ee10b089dfc9bb92171710
Differential Revision: D15118978
Pulled By: suo
fbshipit-source-id: f2b487fd65520d1b7f45cb74145634d334ef1614
