Support parsing variadic return schema (#23199)
Summary:
all cases should be prim ops, but let's support it. it will expect variadic return schema to be prim::PythonOp(...) -> ...
Pull Request resolved: https://github.com/pytorch/pytorch/pull/23199
ghstack-source-id: 87113845
Differential Revision: D16431635
fbshipit-source-id: 798b6957ce5d800f7fcf981c86fdcb009cd77a78
