docs: def get_flag_record(self, feature_key: str) -> str:
          """Get feature flag record from redis.
  
          :param feature_key: key for feature flag
  
          :return: value of feature flag key in redis.
  
          :raises: KeyError if key is not found.
          """
          key_name = self._format_key_name()
          flag = self.redis.hget(key_name, feature_key)
  
          if flag is None:
              raise KeyError('Redis key: {0} not found.'.format(key_name))
  
          return flag