code: def setUp(self):
      if (
          self.iterator_class == chainer.iterators.MultiprocessIterator
          and int(platform.python_version_tuple()[0]) < 3
      ):
          pytest.skip("This test requires Python version >= 3")
      self.communicator = chainermn.create_communicator("naive")
  
      if self.communicator.size < 2:
          pytest.skip("This test is for multinode only")
  
      self.N = 100
      if self.paired_dataset:
          self.dataset = list(
              zip(
                  np.arange(self.N).astype(np.float32),
                  np.arange(self.N).astype(np.float32),
              )
          )
      else:
          self.dataset = np.arange(self.N).astype(np.float32)
  
imports: import chainer
  import chainer.testing
  import chainer.testing.attr
  import chainermn
  from chainermn.iterators.multi_node_iterator import _build_ctrl_msg
  from chainermn.iterators.multi_node_iterator import _parse_ctrl_msg
  import numpy
  import platform
  import pytest
  from six.moves import range
  import unittest
label_desc: Use image node_id 1 for calling the TestMultiNodeIterator obj's underlying member method code with example usage: obj.setUp() without return types