def new_uid_validity(cls) -> int:
        """Generate a new UID validity value for a mailbox, where the first
        two bytes are time-based and the second two bytes are random.

        """
        time_part = int(time.time()) % 4096
        rand_part = random.randint(0, 1048576)
        return (time_part << 20) + rand_part
Generate a new UID validity value for a mailbox, where the first
        two bytes are time-based and the second two bytes are random.