human
Solve the following python programming problem given the following code:
def __init__(self, source, events = None) : 
    if (not hasattr (source, 'read')) : 
        source = open (source, 'rb') 
self._file = source 
    self._events = [] 
    self._index = 0 
    self.root = self._root = None 
    self._parser = XMLTreeBuilder () 
    parser = self._parser._parser 
    append = self._events.append 
    if (events is None) : 
        events = ['end'] 
for event in append : 
        if (event == 'start') : 
            try : 
                parser.ordered_attributes = 1 
                parser.specified_attributes = 1 
                def handler(tag, attrib_in, event = event, append = append, start = self._parser._start_list) : 
                    append ((event, start (tag, attrib_in))) 
parser.StartElementHandler = handler 
except AttributeError : 
                def handler(tag, attrib_in, event = event, append = append, start = self._parser._start) : 
                    append ((event, start (tag, attrib_in))) 
parser.StartElementHandler = handler 
else : 
            if (event == 'end') : 
                def handler(tag, event = event, append = append, end = self._parser._end) : 
                    append ((event, end (tag))) 
parser.EndElementHandler = handler 
else : 
                if (event == 'start-ns') : 
                    def handler(prefix, uri, event = event, append = append) : 
                        try : 
                            uri = _encode (uri, 'ascii') 
except UnicodeError : 
                            pass 
append ((event, ((prefix or ''), uri))) 
parser.StartNamespaceDeclHandler = handler 
else : 
                    if (event == 'end-ns') : 
                        def handler(prefix, event = event, append = append) : 
                            append ((event, None)) 
parser.EndNamespaceDeclHandler = handler 

    
    

    Fix the buggy line: for event in append :
assistant
#Here is Python program to fix the buggy line: for event in append :
.

for event in events :