code: def testStopGradient(self):
      stop_gradient = mtf.StopGradient(self.x)
      self.assertEqual(
          stop_gradient.splittable_dims, frozenset(["a", "b"])
      )
      self.assertEqual(stop_gradient.unsplittable_dims, frozenset())
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from absl.testing import parameterized
  import mesh_tensorflow
  from mesh_tensorflow import test_utils
  import numpy
  import tensorflow.compat.v1
  from tensorflow.python.framework import test_util
label_desc: Use image node_id 23 for calling the OperationSplittabilityTest obj's underlying member method code with example usage: obj.testStopGradient() without return types