action='store_const', dest='format', help='download all available video formats', const='all')
video_format.add_option('--max-quality',
action='store', dest='format_limit', metavar='FORMAT', help='highest quality format to download')
action='store_const', dest='format', help='download all available video formats', const='all')
video_format.add_option('--max-quality',
action='store', dest='format_limit', metavar='FORMAT', help='highest quality format to download')