code: def test_multi_node_batch_normalization_forward_gpu(self):
      self.l.to_gpu()
      self.check_forward(cuda.to_gpu(self.x))
  
imports: import unittest
  import numpy
  import chainer
  from chainer.backends import cuda
  from chainer.functions import relu
  from chainer import testing
  from chainermn import create_communicator
  from chainercv.links.model.mobilenet import TFConv2DBNActiv
  from chainercv.utils.testing import attr
label_desc: Use image node_id 4 for calling the TestTFConv2DMultiNodeBNActiv obj's underlying member method code with example usage: obj.test_multi_node_batch_normalization_forward_gpu() without return types