code: def lset(self, key, index, value):
          
          redis_list = self._get_list(key, 'LSET')
          if redis_list is None:
              raise ResponseError("no such key")
          try:
              redis_list[index] = self._encode(value)
          except IndexError:
              raise ResponseError("index out of range")
docs: Emulate lset.