code: def test_diff():
      config = TestConfig(**good)
      assert diff(config, good_config) == ""
      another = deepcopy(good)
      another["msg"] = "another"
      assert "another/b" in diff(config, TestConfig(**another))
  
file_path: nni/test/ut/experiment/test_config_base.py
imports: from copy import deepcopy
  from dataclasses import dataclass
  from typing import Dict, List, Optional, Union
  from nni.experiment.config.base import ConfigBase
  from nni.experiment.config.utils import diff
label_desc: Use image node_id 3 for calling a global function with example usage: test_diff() without return types