[DataPipe] Improve inline doc and testing for CollatorIterDataPipe (#70139)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/70139
cc VitalyFedyunin ejguan NivekT
Test Plan: Imported from OSS
Reviewed By: ejguan
Differential Revision: D33199107
Pulled By: NivekT
fbshipit-source-id: f96d77490998ac9bc3da8d4ff1a9caa08e9e7f27
