docs: def DualDBSystemCronJob(legacy_name=None, stateful=False):
    """Decorator that creates AFF4 and RELDB cronjobs from a given mixin."""
  
    def Decorator(cls):
      """Decorator producing 2 classes: legacy style one and a new style one."""
      if not legacy_name:
        raise ValueError("legacy_name has to be provided")
  
      # Legacy cron jobs have different base classes depending on whether they're
      # stateful or not.
      if stateful:
        aff4_base_cls = StatefulSystemCronFlow
      else:
        aff4_base_cls = SystemCronFlow
  
      # Make sure that we're dealing with a true mixin to avoid subtle errors.
      if issubclass(cls, cronjobs.SystemCronJobBase):
        raise ValueError("Mixin class shouldn't inherit from SystemCronJobBase")
  
      if issubclass(cls, aff4_base_cls):
        raise ValueError("Mixin class shouldn't inherit from %s" %
                         aff4_base_cls.__name__)
  
      # Generate legacy class. Register it within the module as it's not going
      # to be returned from the decorator.
      aff4_cls = compatibility.MakeType(
          legacy_name, (cls, LegacyCronJobAdapterMixin, aff4_base_cls), {})
      module = sys.modules[cls.__module__]
      setattr(module, legacy_name, aff4_cls)
  
      # Generate new class. No need to register it in the module (like the legacy
      # one) since it will replace the original decorated class.
      reldb_cls = compatibility.MakeType(
          compatibility.GetName(cls), (cls, cronjobs.SystemCronJobBase), {})
      return reldb_cls
  
    return Decorator