Enforce single parent for script submodules (#18379) (#18860)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/18860
ghimport-source-id: 96305349bf3db564f43df2263b1e5bddcc9e9dae
Reviewed By: suo
Differential Revision: D14780421
Pulled By: zdevito
fbshipit-source-id: 2bdd89b35866ba035ebea0adab037e441c1006e2
