Make PythonPrint a class (#26787)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/26787
A follow up PR will remove the need to issue import statements,
or write classes in order since they are no longer needed.
This change allows the same PythonPrint class
to be used for an entire file which will be needed in that patch.
Test Plan: Imported from OSS
Differential Revision: D17566440
Pulled By: zdevito
fbshipit-source-id: 1ee896da0cdfe6a003298e1d4b0238403b9ed6dd
