docs: def init_db_conn(
          connection_name, HOST=None, PORT=None, DB=None, PASSWORD=None):
      """
      Initialize a redis connection by each connection string
      defined in the configuration file
      """
      rpool = redis.ConnectionPool(
          host=HOST, port=PORT, db=DB, password=PASSWORD)
      r = redis.Redis(connection_pool=rpool)
      redis_pool.connections[connection_name] = RedisClient(r)