Rename 'not_differentiable' to 'non_differentiable'. (#19272)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/19272
ghimport-source-id: 755e91efa68c5a1c4377a6853f21b3eee3f8cab5
Differential Revision: D15003381
Pulled By: gchanan
fbshipit-source-id: 54db27c5c5e65acf65821543db3217de9dd9bdb5
