code: def test_pooling_undefined_output_shape(self):
      max_pool_layer = layers.MaxPooling((2, 2))
      self.assertShapesEqual(
          max_pool_layer.output_shape, (None, None, None, None)
      )
  
imports: from collections import namedtuple
  import numpy
  import tensorflow
  from neupy import layers
  from neupy.utils import asfloat
  from neupy.exceptions import LayerConnectionError
  from neupy.layers.pooling import pooling_output_shape
  from base import BaseTestCase
label_desc: Use image node_id 3 for calling the PoolingLayersTestCase obj's underlying member method code with example usage: obj.test_pooling_undefined_output_shape() without return types