get location of coverart

dear rhytmbox-dev team !

I started writing a simple python-plugin to embedd coverart into the 
music-files,
for that I need the location of the cover-art.
As far I could see, in the cache there is always a copy of the displayed 
cover-art.

from the python-console:

entry=shell.get_player().get_playing_entry()
image=shell.props.db.entry_get(entry, rhythmdb.PROP_IMAGE)

will not work.....

does that mean the coverart uri is not stored in rhythmbd ?
do I really need to patch the artdisplay plugin for this simple task ?

thanks in advance and sorry for this newbie question.

gebi