Add assert_async (#53086)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/53086
Fixes #36853
Signed-off-by: Edward Z. Yang <ezyang@fb.com>
Test Plan: Imported from OSS
Reviewed By: albanD
Differential Revision: D26744062
Pulled By: ezyang
fbshipit-source-id: be6d2653afe584adf67a05b5d43185b40764650d
