of biting the hand that has finally , to some extent , warmed up to him 
(ROOT (PP (IN of) (S (VP (VBG biting) (NP (NP (DT the) (NN hand)) (SBAR (WHNP (WDT that)) (S (VP (VBZ has) (ADVP (RB finally)) (, ,) (PP (IN to) (NP (DT some) (NN extent))) (, ,) (VP (VBN warmed) (PRT (RP up)) (PP (IN to) (NP (PRP him))))))))))))
(ROOT (PP (IN ) (S (VP (VBG ) (NP (NP (DT ) (NN )) (SBAR (WHNP (WDT )) (S (VP (VBZ ) (ADVP (RB )) (, ) (PP (IN ) (NP (DT ) (NN ))) (, ) (VP (VBN ) (PRT (RP )) (PP (IN ) (NP (PRP ))))))))))))