human
Solve the following python programming problem given the following code:
@ property 
def nspfxs(self) : 
    '
        A sequence containing each of the namespace prefixes appearing in
        this tree. Each prefix appears once and only once, and in document
        order.
        ' 
    def merge(seq, seq_2) : 
        for item in seq_2 : 
            if (item in seq) : 
                continue 
seq.append (item) 
nspfxs = child.local_nspfxs 
    for child in self._children : 
        merge (nspfxs, child.nspfxs) 
return nspfxs 

    
    

    Fix the buggy line: nspfxs = child.local_nspfxs
assistant
#Here is Python program to fix the buggy line: nspfxs = child.

nspfxs = self.local_nspfxs