Return an element instantiated from the information that a music
        service has (alternative constructor)

        Args:
            music_service (MusicService): The music service that content_dict
                originated from
            content_dict (OrderedDict): The data to instantiate the music
                service item from

        Returns:
            MusicServiceItem: A MusicServiceItem instance

def from_music_service(cls, music_service, content_dict):
        """Return an element instantiated from the information that a music
        service has (alternative constructor)

        Args:
            music_service (MusicService): The music service that content_dict
                originated from
            content_dict (OrderedDict): The data to instantiate the music
                service item from

        Returns:
            MusicServiceItem: A MusicServiceItem instance
        """
        # Form the item_id
        quoted_id = quote_url(content_dict['id'].encode('utf-8'))
        # The hex prefix remains a mistery for now
        item_id = '0fffffff{}'.format(quoted_id)
        # Form the uri
        is_track = cls == get_class('MediaMetadataTrack')
        uri = form_uri(item_id, music_service, is_track)
        # Form resources and get desc
        resources = [DidlResource(uri=uri, protocol_info="DUMMY")]
        desc = music_service.desc
        return cls(item_id, desc, resources, uri, content_dict,
                   music_service=music_service)