More robust check of whether a class is defined in torch (#64083)
Summary:
This would prevent bugs for classes that
1) Is defined in a module that happens to start with `torch`, say `torchvision`
2) Is defined in torch but with an import alias like `import torch as th`
Pull Request resolved: https://github.com/pytorch/pytorch/pull/64083
Reviewed By: soulitzer
Differential Revision: D30598369
Pulled By: gmagogsfm
fbshipit-source-id: 9d3a7135737b2339c9bd32195e4e69a9c07549d4
