I feel like I’m much closer to getting this all to work, thanks to the advice here.  The issue I seem to be having now is that when I set DataLoader’s num_workers > 0, I receive a warning and the loader never returns any data.  if num_workers=0 then it works as expected.
I am on a Mac.
Python 3.7.3
torch==1.8.0

Here is my warning/error:
Warning: Cannot set number of intraop threads after parallel work has started or after set_num_threads call when using native parallel backend (function set_num_threads)
Could this be due to the fact I am using a Jupyter notebook, which is perhaps already taking control of the thread process?  Or do I need to set some other parameters to prepare for the dataloader to properly multithread?