Thanks for the quick reply.
The DataLoader is a necessity, actually, but also a very nice concept to work with.
I just tested the code, but it still fails - the error is below.
Running with num_workers=0 return no errors.
RuntimeError: DataLoader worker (pid 30756) exited unexpectedly with exit code 1. Details are lost due to multiprocessing. Rerunning with num_workers=0 may give better error trace.