@classmethod
def __find_last_mp3_frame__(cls, mp3file):
    """places mp3file at the position of the last MP3 frame's end

        (either the last byte in the file or just before the ID3v1 tag)
        this may not be strictly accurate if ReplayGain data is present,
        since APEv2 tags came before the ID3v1 tag,
        but we're not planning to change that tag anyway
        """
    mp3file.seek(-128, 2)
    if mp3file.read(3) == b'TAG':
        mp3file.seek(-128, 2)
        return
    else:
        mp3file.seek(0, 2)
    return
