docs: def as_subbundle(cls, name=None, title=None, title_plural=None):
          """
          Wraps the given bundle so that it can be lazily
          instantiated.
  
          :param name: The slug for this bundle.
          :param title: The verbose name for this bundle.
          """
          return PromiseBundle(cls, name=name, title=title,
                                  title_plural=title_plural)