I have a dataset whose labels are from 0 to 39. And i wrap it using torch.utils.data.DataLoader, if i set num_workers to be 0, everything works fine, However if it is set to be 2, then the labels batch (a 1-D byte tensor)it loads at some epoch always seems to be bigger than 39, which seems to be 255. what causes this problem? any help? ( P.S. my dataset is .h5 file).