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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 get_ffmpeg_exe():
 """ Return path to ffmpeg executable """

    if 'FFMPEG_PATH' in os.environ:
        ffmpeg_exe = os.environ['FFMPEG_PATH']
    else:
        ffmpeg_exe = which('ffmpeg')

    if not ffmpeg_exe:
        if which('avconv'):
            raise FFmpegNormalizeError(
                "avconv is not supported. "
                "Please install ffmpeg from http://ffmpeg.org instead."
            )
        else:
            raise FFmpegNormalizeError(
                "Could not find ffmpeg in your $PATH or $FFMPEG_PATH. "
                "Please install ffmpeg from http://ffmpeg.org"
            )

    return ffmpeg_exe