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* PPIDataset

* Revert "PPIDataset"

This reverts commit 264bd0c960cfa698a7bb946dad132bf52c2d0c8a.

* Revert "Revert "PPIDataset""

This reverts commit 6938a4cbe3ac6e38d3e0188b5699e5c952a6102e.

* update doc string
Co-authored-by: xiang song(charlie.song) <classicxsong@gmail.com>