How to use the miniaudio.DuplexStream function in miniaudio

def test_stop_callback_duplex(backends, jackd_server):
    stop_callback = mock.Mock()

    duplex = miniaudio.DuplexStream(backends=backends)
    gen = dummy_generator()
    next(gen)
    duplex.start(gen, stop_callback)

    assert duplex.running is True
    # Simulate an unexpected stop.
    miniaudio.lib.ma_device_stop(duplex._device)

    stop_callback.assert_called_once()
    assert duplex.running is False

playbacks = devices.get_playbacks()
    for d in enumerate(playbacks, 1):
        print("{num} = {name}".format(num=d[0], name=d[1]['name']))
    playback_choice = int(input("play on which device? "))
    return captures[capture_choice-1], playbacks[playback_choice-1]


if __name__ == "__main__":
    def pass_through():
        data = yield b""
        while True:
            print(".", end="", flush=True)
            data = yield data

    capture_dev, playback_dev = choose_devices()
    duplex = miniaudio.DuplexStream(sample_rate=48000, backends=backends,
                                    playback_device_id=playback_dev["id"], capture_device_id=capture_dev["id"])
    generator = pass_through()
    next(generator)
    print("Starting duplex stream. Press Ctrl + C to exit.")
    duplex.start(generator)

    running = True
    while running:
        try:
            sleep(1)
        except KeyboardInterrupt:
            running = False
    duplex.stop()