Serialize first-class version of functions (#19723)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/19723
ghimport-source-id: 7f7ec6200c3b42d19046a3e228a3d82212697f14
Reviewed By: jamesr66a
Differential Revision: D15078533
Pulled By: zdevito
fbshipit-source-id: fe421afab9607ee942f6d200f04bb6335fc0aa97
