digraph g {
	Start [shape=box];
	l2 [label="a = 10"];
	l3 [label="b = 20"];
	l4 [label="f(a, b)"];
	p1 [label="x_in = a"];
	p2 [label="y_in = b"];
	p3 [label="a = x_out"];
	l5 [label="print(a)"];
	// Rank
	{ rank = same; l2; l3; l4; l5; }
	{ rank = min; Start; }
	{ rank = same; p1; p2; p3; }
	// Control
	{ edge [style = bold];
		Start -> { l2 l3 l4 l5 };
		l4 -> { p1 p2 p3 };
	}
	// Data
	{ edge [color = red];
		l2 -> p1;
		l3 -> p2;
		p3 -> l5;
	}
	// Order
	{ edge [style = invis];
		l2 -> l3 -> l4 -> l5;
		p1 -> p2 -> p3;
	}
}