Some small fixes for NamedTuple (#21813)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/21813
ghimport-source-id: a1edca8ad0384a9e493ef2f3b0aa5005a668a8f3
Test Plan: Imported from OSS
Reviewed By: zdevito
Differential Revision: D15860005
Pulled By: jamesr66a
fbshipit-source-id: 4a43432d2dacebde1a676a93ac57f675db857154
