code: def setUp(self):
      self.mpi_comm = mpi4py.MPI.COMM_WORLD
      self.communicator = NaiveCommunicator(self.mpi_comm)
  
imports: from __future__ import with_statement
  import itertools
  import unittest
  import mpi4py.MPI
  import numpy
  import pytest
  from chainer import testing
  import chainermn
  from chainermn.communicators.flat_communicator import FlatCommunicator
  from chainermn.communicators.naive_communicator import NaiveCommunicator
  import chainerx
label_desc: Use image node_id 1 for calling the TestDataset obj's underlying member method code with example usage: obj.setUp() without return types