yet , it must be admitted , not entirely humorless 
(ROOT (S (ADVP (RB yet)) (PRN (, ,) (S (NP (PRP it)) (VP (MD must) (VP (VB be) (VP (VBN admitted))))) (, ,)) (ADJP (RB not) (RB entirely) (JJ humorless))))
(ROOT (S (ADVP (RB )) (PRN (, ) (S (NP (PRP )) (VP (MD ) (VP (VB ) (VP (VBN ))))) (, )) (ADJP (RB ) (RB ) (JJ ))))