flog the dead horse of surprise as if it were an obligation 
(ROOT (S (VP (VB flog) (NP (NP (DT the) (JJ dead) (NN horse)) (PP (IN of) (NP (NN surprise)))) (SBAR (IN as) (IN if) (S (NP (PRP it)) (VP (VBD were) (NP (DT an) (NN obligation))))))))
(ROOT (S (VP (VB ) (NP (NP (DT ) (JJ ) (NN )) (PP (IN ) (NP (NN )))) (SBAR (IN ) (IN ) (S (NP (PRP )) (VP (VBD ) (NP (DT ) (NN ))))))))