(CP 
  (WHNP-1 
    (-NONE- *OP*))
                    
  (CP 
    (IP 
      (NP-TPC 
        (-NONE- *T*-1))
                    
      (NP-SBJ 
        (-NONE- *pro*))
                    
      (VP 
        (VV 匿藏)
                    
        (PP 
          (P 在)
                    
          (NP 
            (NN 背后)))))
                    
    (DEC 的)))
                    
(NP 
  (NN 西瓜)
                    
  (NN 刀))))
arg0: 
                    *pro*          
                
arg1: 
                    *T*-1 -> 西瓜 刀          
                
arg2: 
                    在 背后