code: def range_by_lex(self, low, high, start=None, num=None, reverse=False):
          
          if reverse:
              fn = self.database.zrevrangebylex
              low, high = high, low
          else:
              fn = self.database.zrangebylex
          return fn(self.key, low, high, start, num)
docs: Return a range of members in a sorted set, by lexicographical range.