code: def test_function_chaining(self):
      def get_one():
          return 1
  
      def f():
          return get_one().__add__(20)
  
      tr, mock = self._transform_with_mock(f)
  
      self.assertEqual(tr(), 21)
      self.assertListEqual(
          mock.calls,
          [
              ((), None),
              ((20,), None),
          ],
      )
  
imports: import types
  from tensorflow.python.autograph.converters import call_trees
  from tensorflow.python.autograph.converters import functions
  from tensorflow.python.autograph.core import converter_testing
  from tensorflow.python.platform import test
label_desc: Use image node_id 5 for calling the CallTreesTest obj's underlying member method code with example usage: obj.test_function_chaining() and returns: int, get_one