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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 RegisterTXXXKey(cls, key, desc):
 """Register a user-defined text frame key. Some ID3 tags are stored in TXXX frames, which allow a freeform 'description' which acts as a subkey, e.g. TXXX:BARCODE.:: EasyID3.RegisterTXXXKey('barcode', 'BARCODE'). """

        frameid = "TXXX:" + desc

        def getter(id3, key):
            return list(id3[frameid])

        def setter(id3, key, value):
            enc = 0
            # Store 8859-1 if we can, per MusicBrainz spec.
            for v in value:
                if v and max(v) > u'\x7f':
                    enc = 3
                    break

            id3.add(mutagen.id3.TXXX(encoding=enc, text=value, desc=desc))

        def deleter(id3, key):
            del(id3[frameid])

        cls.RegisterKey(key, getter, setter, deleter)