question: adding a 1-d array `[1, 2, 3, 4, 5, 6, 7, 8, 9]` to a 3-d array `np.zeros((6, 9, 20))`
  
target: np . zeros ( ( 6 , 9 , 20 ) ) + np . array ( [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ] ) [ ( None ) , : , ( None ) ] 
  