human
Solve the following python programming problem given the following code:
def filter(self, filter) : 
    '
        Apply filter on this node iterator, and return a new iterator instead.
        `filter` should be a Filter instance.
        ' 
    if (filter is not None) : 
        assert isinstance (self, filters.Filter) 
        def new_iterator() : 
            for n in self : 
                if filter._filter (n) : 
                    (yield n) 
return NodeIterator (new_iterator) 
else : 
        return self 

    
    

    Fix the buggy line: assert isinstance (self, filters.Filter)
assistant
#Here is Python program to fix the buggy line: assert isinstance (self, filters.

assert isinstance (filter, filters.Filter)