code: def test_object_tracker(self):
      test_case.skip_if_not_tf2("Tensorflow 2.x required")
  
      trackable_object = tf.__internal__.tracking.Trackable()
  
      @tf.function
      def preprocessing_fn():
          _ = annotators.make_and_track_object(lambda: trackable_object)
          return 1
  
      object_tracker = annotators.ObjectTracker()
      with annotators.object_tracker_scope(object_tracker):
          _ = preprocessing_fn()
  
      self.assertLen(object_tracker.trackable_objects, 1)
      self.assertEqual(
          trackable_object, object_tracker.trackable_objects[0]
      )
  
imports: import tensorflow
  from tensorflow_transform import annotators
  from tensorflow_transform import test_case
label_desc: Use image node_id 2 for calling the AnnotatorsTest obj's underlying member method code with example usage: obj.test_object_tracker() and returns: int