How to use the mediafile.MP3StorageStyle function in mediafile

def setUp(self):
        self.create_temp_dir()
        self.key = "READ_ONLY_TEST"
        self.field = mediafile.MediaField(
            mediafile.MP3StorageStyle(self.key, read_only=True),
            mediafile.MP4StorageStyle(
                "----:com.apple.iTunes:" + self.key, read_only=True),
            mediafile.StorageStyle(self.key, read_only=True),
            mediafile.ASFStorageStyle(self.key, read_only=True),
        )

        if "read_only_test" not in mediafile.MediaFile.fields():
            mediafile.MediaFile.add_field("read_only_test", self.field)

For any key in `dict` that is also a field to store tags the
        method retrieves the corresponding value from `dict` and updates
        the `MediaFile`. If a key has the value `None`, the
        corresponding property is deleted from the `MediaFile`.
        """
        for field in self.sorted_fields():
            if field in dict:
                if dict[field] is None:
                    delattr(self, field)
                else:
                    setattr(self, field, dict[field])

    # Field definitions.

    title = MediaField(
        MP3StorageStyle('TIT2'),
        MP4StorageStyle('\xa9nam'),
        StorageStyle('TITLE'),
        ASFStorageStyle('Title'),
    )
    artist = MediaField(
        MP3StorageStyle('TPE1'),
        MP4StorageStyle('\xa9ART'),
        StorageStyle('ARTIST'),
        ASFStorageStyle('Author'),
    )
    album = MediaField(
        MP3StorageStyle('TALB'),
        MP4StorageStyle('\xa9alb'),
        StorageStyle('ALBUM'),
        ASFStorageStyle('WM/AlbumTitle'),
    )

# Release date.
    date = DateField(
        MP3StorageStyle('TDRC'),
        MP4StorageStyle('\xa9day'),
        StorageStyle('DATE'),
        ASFStorageStyle('WM/Year'),
        year=(StorageStyle('YEAR'),))

    year = date.year_field()
    month = date.month_field()
    day = date.day_field()

    # *Original* release date.
    original_date = DateField(
        MP3StorageStyle('TDOR'),
        MP4StorageStyle('----:com.apple.iTunes:ORIGINAL YEAR'),
        StorageStyle('ORIGINALDATE'),
        ASFStorageStyle('WM/OriginalReleaseYear'))

    original_year = original_date.year_field()
    original_month = original_date.month_field()
    original_day = original_date.day_field()

    # Nonstandard metadata.
    artist_credit = MediaField(
        MP3DescStorageStyle(u'Artist Credit'),
        MP4StorageStyle('----:com.apple.iTunes:Artist Credit'),
        StorageStyle('ARTIST_CREDIT'),
        ASFStorageStyle('beets/Artist Credit'),
    )
    albumartist_credit = MediaField(

MP3DescStorageStyle(key='COMM'),
        MP4StorageStyle('\xa9cmt'),
        StorageStyle('DESCRIPTION'),
        StorageStyle('COMMENT'),
        ASFStorageStyle('WM/Comments'),
        ASFStorageStyle('Description')
    )
    bpm = MediaField(
        MP3StorageStyle('TBPM'),
        MP4StorageStyle('tmpo', as_type=int),
        StorageStyle('BPM'),
        ASFStorageStyle('WM/BeatsPerMinute'),
        out_type=int,
    )
    comp = MediaField(
        MP3StorageStyle('TCMP'),
        MP4BoolStorageStyle('cpil'),
        StorageStyle('COMPILATION'),
        ASFStorageStyle('WM/IsCompilation', as_type=bool),
        out_type=bool,
    )
    albumartist = MediaField(
        MP3StorageStyle('TPE2'),
        MP4StorageStyle('aART'),
        StorageStyle('ALBUM ARTIST'),
        StorageStyle('ALBUMARTIST'),
        ASFStorageStyle('WM/AlbumArtist'),
    )
    albumtype = MediaField(
        MP3DescStorageStyle(u'MusicBrainz Album Type'),
        MP4StorageStyle('----:com.apple.iTunes:MusicBrainz Album Type'),
        StorageStyle('RELEASETYPE'),

ASFStorageStyle('WM/CatalogNo'),
    )
    barcode = MediaField(
        MP3DescStorageStyle(u'BARCODE'),
        MP4StorageStyle('----:com.apple.iTunes:BARCODE'),
        StorageStyle('BARCODE'),
        ASFStorageStyle('WM/Barcode'),
    )
    disctitle = MediaField(
        MP3StorageStyle('TSST'),
        MP4StorageStyle('----:com.apple.iTunes:DISCSUBTITLE'),
        StorageStyle('DISCSUBTITLE'),
        ASFStorageStyle('WM/SetSubTitle'),
    )
    encoder = MediaField(
        MP3StorageStyle('TENC'),
        MP4StorageStyle('\xa9too'),
        StorageStyle('ENCODEDBY'),
        StorageStyle('ENCODER'),
        ASFStorageStyle('WM/EncodedBy'),
    )
    script = MediaField(
        MP3DescStorageStyle(u'Script'),
        MP4StorageStyle('----:com.apple.iTunes:SCRIPT'),
        StorageStyle('SCRIPT'),
        ASFStorageStyle('WM/Script'),
    )
    language = MediaField(
        MP3StorageStyle('TLAN'),
        MP4StorageStyle('----:com.apple.iTunes:LANGUAGE'),
        StorageStyle('LANGUAGE'),
        ASFStorageStyle('WM/Language'),

bpm = MediaField(
        MP3StorageStyle('TBPM'),
        MP4StorageStyle('tmpo', as_type=int),
        StorageStyle('BPM'),
        ASFStorageStyle('WM/BeatsPerMinute'),
        out_type=int,
    )
    comp = MediaField(
        MP3StorageStyle('TCMP'),
        MP4BoolStorageStyle('cpil'),
        StorageStyle('COMPILATION'),
        ASFStorageStyle('WM/IsCompilation', as_type=bool),
        out_type=bool,
    )
    albumartist = MediaField(
        MP3StorageStyle('TPE2'),
        MP4StorageStyle('aART'),
        StorageStyle('ALBUM ARTIST'),
        StorageStyle('ALBUMARTIST'),
        ASFStorageStyle('WM/AlbumArtist'),
    )
    albumtype = MediaField(
        MP3DescStorageStyle(u'MusicBrainz Album Type'),
        MP4StorageStyle('----:com.apple.iTunes:MusicBrainz Album Type'),
        StorageStyle('RELEASETYPE'),
        StorageStyle('MUSICBRAINZ_ALBUMTYPE'),
        ASFStorageStyle('MusicBrainz/Album Type'),
    )
    label = MediaField(
        MP3StorageStyle('TPUB'),
        MP4StorageStyle('----:com.apple.iTunes:LABEL'),
        MP4StorageStyle('----:com.apple.iTunes:publisher'),

MP3DescStorageStyle(
            u'R128_ALBUM_GAIN'
        ),
        MP4StorageStyle(
            '----:com.apple.iTunes:R128_ALBUM_GAIN'
        ),
        StorageStyle(
            u'R128_ALBUM_GAIN'
        ),
        ASFStorageStyle(
            u'R128_ALBUM_GAIN'
        ),
    )

    initial_key = MediaField(
        MP3StorageStyle('TKEY'),
        MP4StorageStyle('----:com.apple.iTunes:initialkey'),
        StorageStyle('INITIALKEY'),
        ASFStorageStyle('INITIALKEY'),
    )

    @property
    def length(self):
        """The duration of the audio in seconds (a float)."""
        return self.mgfile.info.length

    @property
    def samplerate(self):
        """The audio's sample rate (an int)."""
        if hasattr(self.mgfile.info, 'sample_rate'):
            return self.mgfile.info.sample_rate
        elif self.type == 'opus':

)
    encoder = MediaField(
        MP3StorageStyle('TENC'),
        MP4StorageStyle('\xa9too'),
        StorageStyle('ENCODEDBY'),
        StorageStyle('ENCODER'),
        ASFStorageStyle('WM/EncodedBy'),
    )
    script = MediaField(
        MP3DescStorageStyle(u'Script'),
        MP4StorageStyle('----:com.apple.iTunes:SCRIPT'),
        StorageStyle('SCRIPT'),
        ASFStorageStyle('WM/Script'),
    )
    language = MediaField(
        MP3StorageStyle('TLAN'),
        MP4StorageStyle('----:com.apple.iTunes:LANGUAGE'),
        StorageStyle('LANGUAGE'),
        ASFStorageStyle('WM/Language'),
    )
    country = MediaField(
        MP3DescStorageStyle(u'MusicBrainz Album Release Country'),
        MP4StorageStyle('----:com.apple.iTunes:MusicBrainz '
                        'Album Release Country'),
        StorageStyle('RELEASECOUNTRY'),
        ASFStorageStyle('MusicBrainz/Album Release Country'),
    )
    albumstatus = MediaField(
        MP3DescStorageStyle(u'MusicBrainz Album Status'),
        MP4StorageStyle('----:com.apple.iTunes:MusicBrainz Album Status'),
        StorageStyle('RELEASESTATUS'),
        StorageStyle('MUSICBRAINZ_ALBUMSTATUS'),