[ONNX] Relax check on Prim::PythonOp nodes for ONNX_FALLTHROUGH (#66172) (#67273)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/67273
* Relax check on Prim::PythonOp nodes for Onnx_fallthrough
* Add tests
Test Plan: Imported from OSS
Reviewed By: msaroufim
Differential Revision: D31962521
Pulled By: malfet
fbshipit-source-id: 878920196d66c4f1dadaf3ebb9a7bf69b88849b4
