:class:`str`: The album cover image URL from Spotify's CDN.

def album_cover_url(self):
        """:class:`str`: The album cover image URL from Spotify's CDN."""
        large_image = self._assets.get('large_image', '')
        if large_image[:8] != 'spotify:':
            return ''
        album_image_id = large_image[8:]
        return 'https://i.scdn.co/image/' + album_image_id