human
Solve the following python programming problem given the following code:
def test_diff_no_eval_derivative() : 
    class My (Expr) : 
        def __new__(cls, x) : 
            return Expr.__new__ (cls, x) 
(x, y) = symbols ('x y') 
    assert (My (x).diff (x).func is Derivative) 
    assert (My (x).diff (x) == 0) 

    
    

    Fix the buggy line: assert (My (x).diff (x) == 0)
assistant
#Here is Python program to fix the buggy line: assert (My (x).

assert (My (x).diff (y) == 0)