Just a quick update:
It looks as though at some point the MultiScaleRoIAlign constructor moved from using a list of indices to a list of keys for featmap_names, while the docstrings weren’t updated to reflect this.
This has been corrected in this commit 32. The correct behavior was being emulated by
roi_pooler = torchvision.ops.MultiScaleRoIAlign(featmap_names=['0'],
                                                output_size=7,
                                                sampling_ratio=2)