traverse is different from PyTorch core and broken

[pmeier]

Amongst other things, 0501f56 added the torchdata/dataloader2/_graph_utils.py module that implements traverse:

data/torchdata/dataloader2/_graph_utils.py

Line 57 in 12cfaf8

def traverse(datapipe: IterDataPipe, only_datapipe: bool = False) -> DataPipeGraph:

Unfortunately, this differs from the one in PyTorch core. It is at least missing the patches that resolved #237. Trying to lint a datapipe that has circular references through the attributes (not a circular graph) fails again: https://github.com/pytorch/vision/runs/6551564325

Instead of re-implementing, could we maybe simply from torch.utils.data.graph import traverse to have a single source of truth?

[ejguan]

Confirmed. We should send a PR to fix it ASAP.