code: def unionstore(self, dest, *others, **kwargs):
          
          keys = [self.key]
          keys.extend([other.key for other in others])
          self.database.zunionstore(dest, keys, **kwargs)
          return self.database.ZSet(dest)
docs: Store the union of the current set and one or more
          others in a new key.
  
          :param dest: the name of the key to store union
          :param others: One or more :py:class:`ZSet` instances
          :returns: A :py:class:`ZSet` referencing ``dest``.