code: def testPadOperation(self):
      pad_operation = mtf.PadOperation(self.x, [7, 2], "a")
      self.assertEqual(pad_operation.splittable_dims, frozenset(["b"]))
      self.assertEqual(
          pad_operation.unsplittable_dims, frozenset(["a"])
      )
  
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 17 for calling the OperationSplittabilityTest obj's underlying member method code with example usage: obj.testPadOperation() without return types