define digraph [X1|X2|X3|X4|X5|X6|X7|X8|X9|Y1|Y2|Y3|Y4|Y5|Y6|Y7|Y8|Y9|
Q1|Q2|Q3|Q4|Q5|Q6|Q7|Q8|Q9|W1|W2|W3|W4|W5|W6|W7|W8|W9];

define nullify X1 -> 0, X2 -> 0, X3 -> 0, X4 -> 0, X5 -> 0, X6 -> 0, X7 -> 0, X8 -> 0, X9 -> 0,
 Q1 -> 0, Q2 -> 0, Q3 -> 0, Q4 -> 0, Q5 -> 0, Q6 -> 0, Q7 -> 0, Q8 -> 0, Q9 -> 0,
 Y1 -> 0, Y2 -> 0, Y3 -> 0, Y4 -> 0, Y5 -> 0, Y6 -> 0, Y7 -> 0, Y8 -> 0, Y9 -> 0,
 W1 -> 0, W2 -> 0, W3 -> 0, W4 -> 0, W5 -> 0, W6 -> 0, W7 -> 0, W8 -> 0, W9 -> 0
 || digraph ?* _ ;

push nullify