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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def libvlc_video_get_spu(p_mi):
    '''Get current video subtitle.
    @param p_mi: the media player.
    @return: the video subtitle selected, or -1 if none.
    '''
    f = _Cfunctions.get('libvlc_video_get_spu', None) or \
        _Cfunction('libvlc_video_get_spu', ((1,),), None,
                    ctypes.c_int, MediaPlayer)
    return f(p_mi)