Assess continued use of TorchData

[atolopko-czi]

The TorchData library that the Census ExperimentDataPipe is implemented upon is no longer being actively developed: pytorch/data#1196.

Note that there are two separate IterDataPipe classes:

• torch.utils.data.datapipes.datapipe.IterDataPipe
• torchdata.datapipes.iter.IterDataPipe

Census API's ExperimentDataPipe uses the latter, currently. Even if we were to simply switch to usingtorch.utils.data.datapipes.datapipe.IterDataPipe, the larger issue is the expectation that TorchData DataPipe "operations" like RandomSplitter and Shuffler are available for use in client code. So we may want to provide equivalent, custom functionality in our ExperimentDataPipe, which would be unfortunate.

We can also keep our implementation "as is", since TorchData isn't being pulled away, it just won't see any improvements.

We certainly need to keep ExperimentDataPipe as an "experimental" Census API until we resolve this issue.