Add feature flag for the autograd.Function extension (#89858)
This PR adds a private runtime feature flag for the feature work we're going
to do with extending autograd.Function. The motivation of the feature flag
is:
- to guard the feature against unsuspecting users
- control the release of the feature to when we are ready to release it
We might not even need the feature flag (because we hope to have the
work done in the next month), but it is good practice and it does touch
currently public API (autograd.Function).
Concretely, "autograd.Function extension" refers to:
- adding an optional `setup_context` staticmethod to autograd.Function
- adding an optional `vmap` staticmethod to autograd.Function
- autograd.Function support for functorch
Test Plan:
- new test that the feature flag works
Pull Request resolved: https://github.com/pytorch/pytorch/pull/89858
Approved by: https://github.com/soulitzer
