code: def test_no_constraints(self):
      grid_warper = AffineGridWarperLayer(
          source_shape=(3, 3), output_shape=(2,)
      )
      self.assertEqual(
          grid_warper.constraints.constraints,
          ((None, None, None), (None, None, None)),
      )
  
imports: from __future__ import absolute_import, print_function, division
  import numpy
  import tensorflow
  from niftynet.layer.grid_warper import AffineGridWarperLayer
  from niftynet.layer.grid_warper import AffineWarpConstraints
  from niftynet.layer.grid_warper import _create_affine_features
  from tests.niftynet_testcase import NiftyNetTestCase
label_desc: Use image node_id 2 for calling the AffineGridWarperLayerTest obj's underlying member method code with example usage: obj.test_no_constraints() without return types