class_docstr: Implementation of the Communicator class via torch.distributed. Use this
  communicator to communicate between different processes, potentially,
  running on different nodes.
docstr: Synchronizes all processes.
  
  This collective blocks processes until the whole group enters this
  function.
code: def barrier(self):
      """Synchronizes all processes.
  
      This collective blocks processes until the whole group enters this
      function.
      """
      assert dist.is_initialized(), "initialize the communicator first"
      dist.barrier(group=self.main_group)
  
imports: import logging
  import os
  import pickle
  import random
  import string
  import numpy
  import torch
  import torch.distributed
  from crypten.common import serial
  from torch.distributed import ReduceOp
  from .communicator import _logging, Communicator
label_desc: Use image node_id 16 for calling the DistributedCommunicator obj's underlying member method code with example usage: obj.barrier() without return types