NamedTuple serialization (#21839)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/21839
ghimport-source-id: b9d82018fbf26b22d58cad3a033cbfe4e879a8fe
Test Plan: Imported from OSS
Reviewed By: zdevito
Differential Revision: D15860002
Pulled By: jamesr66a
fbshipit-source-id: 0fc97c4adefa9ae4937f21179c7afa817f4099e5
