refactor manual function definitions (#43711)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/43711
this makes them available in forward if needed
No change to the file content, just a copy-paste.
Test Plan: Imported from OSS
Reviewed By: mrshenli
Differential Revision: D23454146
Pulled By: albanD
fbshipit-source-id: 6269a4aaf02ed53870fadf8b769ac960e49af195
