code: def difference(self, *others):
          
          others = self._typesafe_others(others)
          return set(map(
              self._loads, self._client.sdiff(self.key_prefix, *others)))
docs: Calculates the difference between this set and @others
  
              @others: one or several #str keynames or :class:RedisSet objects
  
              -> set resulting from the difference between the first set and
                  all @others.