Right, so my understanding of how to handle varying length sequences was to have a max length of the targets (12, in this case), and then pad with the blank label at the end, and have a tensor for the length of each of the targets.  Is there a better way to handle variable length targets without padding?
I don’t think the blank label should be within the target lengths at all, except for the cases where there’s no labels.  I think I tried setting the target length to 0 for those at one point instead of 1, but it threw an error.
This dataset works well enough in Keras where I originally prototyped it.  I think the main change in specification there is that Keras has the blank label not in the label set (i.e., blank_ind = len(labels)) whereas Pytorch requires the blank label be in the label set, correct?