docs: def DatabaseEnabled(cls):
      """Given persistence methods to classes with this annotation.
  
      All this really does is add some functions that forward to the mapped
      database class.
      """
      if not issubclass(cls, Storable):
          raise ValueError(
              "%s is not a subclass of gludb.datab.Storage" % repr(cls)
          )
  
      cls.ensure_table = classmethod(_ensure_table)
      cls.find_one = classmethod(_find_one)
      cls.find_all = classmethod(_find_all)
      cls.find_by_index = classmethod(_find_by_index)
      cls.save = _save
      cls.delete = _delete
  
      return cls