change to multiset approach. need to add edge cases to test code; think they're handled
change to multiset approach. need to add edge cases to test code; think they're handled

nvbn/Unofficial-Google-Music-API,thebigmunch/gmusicapi,tanhaiwang/gmusicapi,simon-weber/Unofficial-Google-Music-API,TheOpenDevProject/gmusicapi,jimyx17/gmusic,simon-weber/gmusicapi,dvirtz/gmusicapi,peetahzee/Unofficial-Google-Music-API,dvirtz/gmusicapi