[DataPipes] Add simple unbatch to DataPipe (#59610)
Summary:
Implements the simple unbatch feature for DataPipe https://github.com/pytorch/pytorch/issues/58148
Pull Request resolved: https://github.com/pytorch/pytorch/pull/59610
Reviewed By: VitalyFedyunin
Differential Revision: D28994180
Pulled By: NivekT
fbshipit-source-id: 4bafe6e26c4f95a808c489b147369413a196fa1c
