code: def test_objective(
      self, objective, expected_objective_fn, metric_fn=None
  ):
      evaluator = Evaluator(input_fn=None, objective=objective)
      self.assertEqual(expected_objective_fn, evaluator.objective_fn)
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from absl.testing import parameterized
  from adanet import tf_compat
  from adanet.core.evaluator import Evaluator
  import adanet.core.testing_utils
  import numpy
  import tensorflow.compat.v2
  from tensorflow.python.eager import context
  from tensorflow.python.framework import test_util
label_desc: Use image node_id 2 for calling the EvaluatorTest obj's underlying member method code with example usage: obj.test_objective(objective, expected_objective_fn, metric_fn) without return types