Add guideline about which dispatch keyword to use in native_functions.yaml. (#46126)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/46126
Test Plan: Imported from OSS
Reviewed By: Krovatkin
Differential Revision: D24233887
Pulled By: ailzhang
fbshipit-source-id: 640543494e0d5211f2f910a75fa2e9bdf558f7ce
