code: def testOverrideEnvVar(self):
      old_home = os.getenv("HOME")
      new_home = self.get_temp_dir()
      with test_case_utils.override_env_var("HOME", new_home):
          self.assertEqual(os.environ["HOME"], new_home)
      self.assertEqual(os.getenv("HOME"), old_home)
  
imports: import copy
  import os
  import unittest
  import tensorflow
  from tfx import types
  from tfx.types import standard_artifacts
  from tfx.utils import test_case_utils
label_desc: Use image node_id 5 for calling the TestCaseUtilsTest obj's underlying member method code with example usage: obj.testOverrideEnvVar() without return types