Revert D27831996: ns for fx: move node I/O dtype mapping to be local instead of global
Test Plan: revert-hammer
Differential Revision:
D27831996 (https://github.com/pytorch/pytorch/commit/93de80203d79615d406e741357172fef11cee29b)
Original commit changeset: 782f5e77de0e
fbshipit-source-id: 6637ef4e8ba76fc4f2b3836ad1ed8d37ce040576
