class_docstr: Implementation of the Communicator class via torch.distributed. Use this
  communicator to communicate between different processes, potentially,
  running on different nodes.
docstr: Gathers tensors from all parties in a list.
code: def all_gather(self, tensor):
      """Gathers tensors from all parties in a list."""
      assert dist.is_initialized(), "initialize the communicator first"
      result = []
      device = tensor.data.device
      for _ in range(self.get_world_size()):
          result.append(
              torch.empty(
                  size=tensor.size(), dtype=torch.long, device=device
              )
          )
      dist.all_gather(result, tensor.data, group=self.main_group)
      return result
  
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 14 for calling the DistributedCommunicator obj's underlying member method code with example usage: obj.all_gather(tensor) and returns: result