Song's foreign_id cache not filled properly, Song.get_foreign_id() not based on tracks

[myselfhimself]

Hello,

Thank you very much for the pyechonest library!!! It is awesome so far : )

To reproduce: call Playlist.static(..., bucket=['id:spotify', 'tracks']) then find that someResultSong.get_foreign_id() returns None although someResultSong.cache['tracks'][0]['foreign_id'] is already filled.

I also noticed that someResultSong.get_foreign_id() also tries to find the foreign_id using only bucket=['id:spotify'](ie.the catalog space) and looking into Song objects... Whereas the right for me would be to have bucket=['id:spotify','tracks'] and look into Song.tracks...

Have a nice day!!! : )