Factor out isDominatedBy (#56437)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/56437
Test Plan: Imported from OSS
Reviewed By: nikithamalgifb
Differential Revision: D27924240
Pulled By: eellison
fbshipit-source-id: d600f895bfb06304957fe65155fceab0e5f873ea
