code: def testTraverserBadNumOutputs(self):
      a = nodes.apply_operation(
          _Constant, value="a", label="Constant[a]"
      )
      mock_visitor = mock.MagicMock()
      mock_visitor.visit.side_effect = [("a", "b")]
  
      with self.assertRaisesRegex(
          ValueError, "has 1 outputs but visitor returned 2 values: "
      ):
          nodes.Traverser(mock_visitor).visit_value_node(a)
  
imports: import tensorflow
  from tensorflow_transform import nodes
  from tensorflow_transform import test_case
  from tfx_bsl.types import tfx_namedtuple
label_desc: Use image node_id 9 for calling the NodesTest obj's underlying member method code with example usage: obj.testTraverserBadNumOutputs() without return types