But Fish is not an upbeat pragmatist.
( But ( Fish ( ( ( is not ) ( an ( upbeat pragmatist ) ) ) . ) ) )
(ROOT (S (CC But) (NP (NN Fish)) (VP (VBZ is) (RB not) (NP (DT an) (JJ upbeat) (NN pragmatist))) (. .)))
Fish is the nickname of a human. 
( Fish ( ( is ( ( the nickname ) ( of ( a human ) ) ) ) . ) )
(ROOT (S (NP (NN Fish)) (VP (VBZ is) (NP (NP (DT the) (NN nickname)) (PP (IN of) (NP (DT a) (NN human))))) (. .)))