human
Solve the following python programming problem given the following code:
def test_position(self) : 
    code = 'def f(x):
    return x + 1' 
    st1 = parser.suite (code) 
    st2 = st1.totuple (line_info = 1, col_info = 1) 
    def walk(tree) : 
        node_type = tree [0] 
        next = tree [1] 
        if isinstance (next, tuple) : 
            for elt in tree [1 :] : 
                for x in walk (elt) : 
                    (yield x) 
else : 
            (yield tree) 
terminals = list (walk (self)) 
    self.assertEqual ([(1, 'def', 1, 0), (1, 'f', 1, 4), (7, '(', 1, 5), (1, 'x', 1, 6), (8, ')', 1, 7), (11, ':', 1, 8), (4, '', 1, 9), (5, '', 2, (- 1)), (1, 'return', 2, 4), (1, 'x', 2, 11), (14, '+', 2, 13), (2, '1', 2, 15), (4, '', 2, 16), (6, '', 2, (- 1)), (4, '', 2, (- 1)), (0, '', 2, (- 1))], terminals) 

    
    

    Fix the buggy line: terminals = list (walk (self))
assistant
#Here is Python code to fix the buggy line: terminals = list (walk (self))
.

terminals = list (walk (st2))