Pytorch DataLoader mulit-process support

[eddyxu]

Problem Statement

As per Pytorch document

https://pytorch.org/docs/stable/data.html#iterable-style-datasets

When num_workers > 0, each worker process will have a different copy of the dataset object, so it is often desired to configure each copy independently to avoid having duplicate data returned from the workers. get_worker_info(), when called in a worker process, returns information about the worker.