code: def set_stat(self, key, value, timeout):
          
          if not self.cache:
              return
          key_list = self.cache.get(Conf.Q_STAT, [])
          if key not in key_list:
              key_list.append(key)
          self.cache.set(Conf.Q_STAT, key_list)
          return self.cache.set(key, value, timeout)
docs: Saves a cluster statistic to the cache provider
          :type key: str
          :type value: str
          :type timeout: int