code: def add(self, _mapping=None, **kwargs):
          
          if _mapping is not None:
              _mapping.update(kwargs)
              mapping = _mapping
          else:
              mapping = _mapping
          return self.database.zadd(self.key, mapping)
docs: Add the given item/score pairs to the ZSet. Arguments are
          specified as ``item1, score1, item2, score2...``.