How should the segmented parts be visualized?
It should be possible to use a filtering approach, by comparing the pixel values of the output segmentation to a specific class index, and get the min/max indices via:
idx = (pred == class_idx).nonzero() 

However, you would usually cut a rectangular segment, which might and most likely will include other classes as well. E.g. the “arm class” might be inside the patch of a segmented “hand class”.