Allow static inheritence for ScriptModules (#20503)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/20503
ghimport-source-id: 35684175f0806485b074ea136548823ad1bc1c30
Differential Revision: D15341555
Pulled By: zdevito
fbshipit-source-id: ad19da3306914196dcbbcee829dcb0a9f22e3722
