Tree based Iterator infrastructure: for in range/list/tensor/zip/enumerate (#21801)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/21801
ghimport-source-id: b019d3e9a6f9bf152991a01b40e424dff176ffaa
Test Plan: Imported from OSS
Differential Revision: D15948545
Pulled By: wanchaol
fbshipit-source-id: 6110a0f3ab08cbbb398441e8330f56083ecd2d99
