https://github.com/NVIDIA/DeepLearningExamples/tree/master/PyTorch/Distributed 102 , This link will open a project where a file multiproc.py is calling through, subprocess.Popen() the main.py file. Where the init_process_group() method is initialized and  torch.nn.parallel.DistributedDataParallel() method is used. Can you explain me the pipeline here? How the different copies of model in different GPU’s are handled and how the data parallelism is handled by these two scripts?