has turned out to be a one-trick pony 
(ROOT (S (NP (VBZ has)) (VP (VBN turned) (PRT (RP out)) (S (VP (TO to) (VP (VB be) (NP (DT a) (NML (CD one) (HYPH -) (NN trick)) (NN pony))))))))
(ROOT (S (NP (VBZ )) (VP (VBN ) (PRT (RP )) (S (VP (TO ) (VP (VB ) (NP (DT ) (NML (CD ) (HYPH ) (NN )) (NN ))))))))