code: def _setup(self):
          
  
          cls = self.__class__
          cls._id_map = {}
          cls._name_map = {}
          for index, info in enumerate(cls._alternatives):
              if len(info) < 3:
                  info = info + ({},)
                  cls._alternatives[index] = info
              id_ = _build_id_tuple(info[2], info[1])
              cls._id_map[id_] = index
              cls._name_map[info[0]] = index
docs: Generates _id_map from _alternatives to allow validating contents