's a rare window on an artistic collaboration 
(ROOT (VP (VBZ 's) (NP (NP (DT a) (JJ rare) (NN window)) (PP (IN on) (NP (DT an) (JJ artistic) (NN collaboration))))))
(ROOT (VP (VBZ ) (NP (NP (DT ) (JJ ) (NN )) (PP (IN ) (NP (DT ) (JJ ) (NN ))))))