How to use the psychtoolbox.audio.buffer function in psychtoolbox

# Wait for sound to stop by itself, block until then:
    startTime, endPositionSecs, xruns, estStopTime = stream.stop()
    print('StartTime', startTime, 'secs. Stop time', estStopTime, 'secs.\n');

    # as before but 1.5*note_freq
    a = np.sin(np.linspace(0, 2 * pi * f * 1.5 * n_samples / Fs))

    # Replicated into two rows - One row for each stereo-channel, ie.
    # m'th row == m'th channel, n'th column = n'th sample frame:
    stereowav2 = [a, a]
    stereowav2 = np.transpose(stereowav2)
    stereowav2 = stereowav2.astype('float32')

    t1 = GetSecs()

    b1 = audio.buffer(stream=stream, data=stereowav2)  # PsychPortAudio('CreateBuffer', pahandle, stereowav2);
    t2 = GetSecs()
    d2 = (1000 * (t2 - t1))
    print('CreateBuffer Duration', d2, ' msecs.')
    t1 = GetSecs()
    b1.fill_buffer(stereowav2)  # PsychPortAudio('FillBuffer', pahandle, b1)
    t2 = GetSecs()
    print('FillBuffer Duration', (1000 * (t2 - t1)), ' msecs.')
    print('d2 / d1 = ', d2 / d1)

    # PsychPortAudio('Start', pahandle, 1, GetSecs() + 1, 1)
    stream.start(when=GetSecs()+1, wait_for_start=1)
    # [startTime, endPositionSecs, xruns, estStopTime] = PsychPortAudio('Stop', pahandle, 1);
    startTime, endPositionSecs, xruns, estStopTime = stream.stop()
    print('StartTime', startTime, 'secs. Stop time', estStopTime, 'secs.\n');

    # Close sound device: