human
Solve the following python programming problem given the following code:
def _tree_example() : 
    root = (((1, 2), (4, 5), 6), (7, 9)) 
    def subn(node) : 
        return (node if isinstance (node, tuple) else ()) 
for path in walk (root, root, event (((enter | exit) | leaf))) : 
        print (list (path), '{0:<7}'.format (event_repr (path.event))) 

    
    

    Fix the buggy line: for path in walk (root, root, event (((enter | exit) | leaf))) :
assistant
#Here is Python program to fix the buggy line: for path in walk (root, root, event (((enter | exit) | leaf))) :
.

for path in walk (root, def subn(, event (((enter | exit) | leaf))) :