use a lambda for singleton field (#680)
use a lambda for singleton field (#680)

Avoids a naming collision for now. We might revert this later with a decorator
approach.

Andypsamp/CODjunit,ttsda/beets,sampsyo/beets,ibmibmibm/beets,mried/beets,kelvinhammond/beets,artemutin/beets,kareemallen/beets,kareemallen/beets,artemutin/beets,shanemikel/beets,Andypsamp/CODjunit,parapente/beets,ttsda/beets,moodboom/beets,SusannaMaria/beets,ibmibmibm/beets,drm00/beets,Freso/beets,lightwang1/beets,kareemallen/beets,mosesfistos1/beetbox,imsparsh/beets,m-urban/beets,multikatt/beets,jmwatte/beets,bj-yinyan/beets,Freso/beets,LordSputnik/beets,marcuskrahl/beets,Andypsamp/CODfinalJUNIT,mosesfistos1/beetbox,shanemikel/beets,sadatay/beets,untitaker/beets,YetAnotherNerd/beets,kelvinhammond/beets,Kraymer/beets,untitaker/beets,lengtche/beets,ttsda/beets,jmwatte/beets,tima/beets,mathstuf/beets,PierreRust/beets,Andypsamp/CODfinalJUNIT,madmouser1/beets,Andypsamp/CODjunit,drm00/beets,moodboom/beets,artemutin/beets,mathstuf/beets,andremiller/beets,randybias/beets,beetbox/beets,mosesfistos1/beetbox,dfc/beets,multikatt/beets,Dishwishy/beets,xsteadfastx/beets,MyTunesFreeMusic/privacy-policy,jcoady9/beets,dfc/beets,SusannaMaria/beets,Kraymer/beets,jackwilsdon/beets,jcoady9/beets,asteven/beets,lengtche/beets,ruippeixotog/beets,jackwilsdon/beets,LordSputnik/beets,diego-plan9/beets,swt30/beets,multikatt/beets,ibmibmibm/beets,LordSputnik/beets,shamangeorge/beets,mried/beets,MyTunesFreeMusic/privacy-policy,Andypsamp/CODfinalJUNIT,tima/beets,jmwatte/beets,untitaker/beets,shamangeorge/beets,ruippeixotog/beets,sampsyo/beets,bj-yinyan/beets,Freso/beets,kelvinhammond/beets,dfc/beets,randybias/beets,swt30/beets,andremiller/beets,tima/beets,sadatay/beets,ruippeixotog/beets,Dishwishy/beets,gabrielaraujof/beets,pkess/beets,SusannaMaria/beets,multikatt/beets,marcuskrahl/beets,beetbox/beets,mosesfistos1/beetbox,swt30/beets,PierreRust/beets,mathstuf/beets,ruippeixotog/beets,Andypsamp/CODjunit,mathstuf/beets,ttsda/beets,LordSputnik/beets,madmouser1/beets,kelvinhammond/beets,madmouser1/beets,Kraymer/beets,Freso/beets,MyTunesFreeMusic/privacy-policy,lengtche/beets,PierreRust/beets,asteven/beets,shamangeorge/beets,imsparsh/beets,Andypsamp/CODfinalJUNIT,swt30/beets,andremiller/beets,m-urban/beets,beetbox/beets,Dishwishy/beets,tima/beets,dfc/beets,Andypsamp/CODfinalJUNIT,beetbox/beets,marcuskrahl/beets,diego-plan9/beets,arabenjamin/beets,diego-plan9/beets,mried/beets,shamangeorge/beets,PierreRust/beets,madmouser1/beets,lengtche/beets,pkess/beets,jackwilsdon/beets,YetAnotherNerd/beets,randybias/beets,YetAnotherNerd/beets,marcuskrahl/beets,MyTunesFreeMusic/privacy-policy,arabenjamin/beets,asteven/beets,imsparsh/beets,m-urban/beets,sampsyo/beets,arabenjamin/beets,SusannaMaria/beets,sadatay/beets,Wen777/beets,untitaker/beets,xsteadfastx/beets,ibmibmibm/beets,diego-plan9/beets,artemutin/beets,bj-yinyan/beets,Andypsamp/CODjunit,mried/beets,m-urban/beets,parapente/beets,Kraymer/beets,asteven/beets,shanemikel/beets,lightwang1/beets,drm00/beets,parapente/beets,gabrielaraujof/beets,moodboom/beets,xsteadfastx/beets,shanemikel/beets,jmwatte/beets,bj-yinyan/beets,jcoady9/beets,sadatay/beets,imsparsh/beets,Wen777/beets,Dishwishy/beets,pkess/beets,YetAnotherNerd/beets,lightwang1/beets,lightwang1/beets,parapente/beets,gabrielaraujof/beets,sampsyo/beets,Wen777/beets,arabenjamin/beets,jackwilsdon/beets,xsteadfastx/beets,pkess/beets,kareemallen/beets,moodboom/beets,randybias/beets,drm00/beets,jcoady9/beets,gabrielaraujof/beets