code: def load_tests(loader, tests, pattern):
      try:
          pure_tests = import_fresh_module(
              TESTS,
              fresh=["datetime", "_pydatetime", "_strptime"],
              blocked=["_datetime"],
          )
          fast_tests = import_fresh_module(
              TESTS,
              fresh=["datetime", "_strptime"],
              blocked=["_pydatetime"],
          )
      finally:
          # XXX: import_fresh_module() is supposed to leave sys.module cache untouched,
          # XXX: but it does not, so we have to cleanup ourselves.
          for modname in ["datetime", "_datetime", "_strptime"]:
              sys.modules.pop(modname, None)
  
      test_modules = [pure_tests, fast_tests]
      test_suffixes = ["_Pure", "_Fast"]
      # XXX(gb) First run all the _Pure tests, then all the _Fast tests.  You might
      # not believe this, but in spite of all the sys.modules trickery running a _Pure
      # test last will leave a mix of pure and native datetime stuff lying around.
      for module, suffix in zip(test_modules, test_suffixes):
          test_classes = []
          for name, cls in module.__dict__.items():
              if not isinstance(cls, type):
                  continue
              if issubclass(cls, unittest.TestCase):
                  test_classes.append(cls)
              elif issubclass(cls, unittest.TestSuite):
                  suit = cls()
                  test_classes.extend(type(test) for test in suit)
          test_classes = sorted(
              set(test_classes), key=lambda cls: cls.__qualname__
          )
          for cls in test_classes:
              cls.__name__ += suffix
              cls.__qualname__ += suffix
  
              @classmethod
              def setUpClass(cls_, module=module):
                  cls_._save_sys_modules = sys.modules.copy()
                  sys.modules[TESTS] = module
                  sys.modules["datetime"] = module.datetime_module
                  if hasattr(module, "_pydatetime"):
                      sys.modules["_pydatetime"] = module._pydatetime
                  sys.modules["_strptime"] = module._strptime
  
              @classmethod
              def tearDownClass(cls_):
                  sys.modules.clear()
                  sys.modules.update(cls_._save_sys_modules)
  
              cls.setUpClass = setUpClass
              cls.tearDownClass = tearDownClass
              tests.addTests(loader.loadTestsFromTestCase(cls))
      return tests
  
label_desc: Use image node_id 1 for calling a global function with example usage: load_tests(loader, tests, pattern) and returns: tests