docs: def union(self, *others):
          """ Calculates union between sets
              @others: one or several :class:RedisSet objects or #str redis set
                  keynames
  
              -> #set of new set members
          """
          others = self._typesafe_others(others)
          return set(map(
              self._loads, self._client.sunion(self.key_prefix, *others)))