code: def test_cudnngbn(self):
      if self.world_size != 2:
          self.skipTest(
              f"This test is written for world_size of 2 but {self.world_size}"
          )
      for shape in input_shapes:
          self._prep()
          self._test_cudnn_gbn(1, shape)
  
imports: import copy
  import typing
  import unittest
  import torch
  import torch.nn
  from torch.testing._internal import common_utils
  from apex.transformer.testing.distributed_test_base import NcclDistributedTestBase
label_desc: Use image node_id 4 for calling the TestCudnnGBN obj's underlying member method code with example usage: obj.test_cudnngbn() without return types