(IP 
  (ADVP 
    (AD 但))
                    
  (NP-SBJ 
    (-NONE- *pro*))
                    
  (VP 
    (VP 
      (VV 知道)
                    
      (IP-OBJ 
        (NP-SBJ 
          (-NONE- *pro*))
                    
        (VP 
          (VPT 
            (VV 起)
                    
            (AD 不)
                    
            (VV 了))
                    
          (NP-OBJ 
            (NN 作用)))))
                    
    (PU ，)
                    
    (VP 
      (ADVP 
        (AD 只))
                    
      (VP 
        (VV 得)
                    
        (VP 
          (ADVP 
            (AD 黯然))
                    
          (VP 
            (VV 回府)))))))
arg0: 
                    *pro* 
                
argm: 
                    黯然 
                
argm: 
                    只 
                
argm: 
                    但