def get(cls, pid, session):
        """Get an idle, unused connection from the pool. Once a connection has
        been retrieved, it will be marked as in-use until it is freed.

        :param str pid: The pool ID
        :param queries.Session session: The session to assign to the connection
        :rtype: psycopg2.extensions.connection

        """
        with cls._lock:
            cls._ensure_pool_exists(pid)
            return cls._pools[pid].get(session)
Get an idle, unused connection from the pool. Once a connection has
        been retrieved, it will be marked as in-use until it is freed.

        :param str pid: The pool ID
        :param queries.Session session: The session to assign to the connection
        :rtype: psycopg2.extensions.connection