[DataPipe] Small change to generation script and update to DataPipe .pyi file (#69392)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/69392
cc VitalyFedyunin ejguan NivekT
Test Plan: Imported from OSS
Reviewed By: ejguan
Differential Revision: D32849463
Pulled By: NivekT
fbshipit-source-id: b6d419fbe0e4cc9d718f21fb3fe886f721f618d3
