I forgot that during clean up.  Basically I wanted to merge my [Advanced Shuffle Client for MPD](https://github.com/pscn/ads) and was hoping to somehow get that to work with relations in beets.  But it won't.  It would require the plugin to have it's on relation database and that was just to heavy.  I'll re-work my other project some other time, but keep it standalone and separate from beets.  However, the mpc plugin let's me keep statistics in beets, which is nice.