Well, I reproduced it locally. Looks like it could not find our internal DLLs because it relies on AddDllDirectory which is not built-in in Python 3.7. There are two workable solutions:

Update to Python 3.8.
Apply https://github.com/pytorch/pytorch/pull/37763 412 manually. Replace your local copy with https://gist.github.com/peterjc123/bcbf4418ff63d88e11313d308cf1b427 276 (e.g. C:\Users\Grace Wu\torchenv\lib\site-packages\torch\__init__.py)