pytorch

1c86b8a7 - add docs for serialization

add docs for serialization Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/23456 Test Plan: Imported from OSS Differential Revision: D16552602 Pulled By: suo fbshipit-source-id: 41e333af97e43fcef2b7f6e02c36a805ceb64573