digraph {
  graph [compound=true, rankdir=BT, ranksep=0.3];
	node [label="\N",
		penwidth=1.5
	];
	edge [penwidth=1.5];

		bottom_left [shape=point, style=invis];
		bottom_right [shape=point, style=invis];
		top_left [shape=point, style=invis];
		top_right [shape=point, style=invis];
		bottom_left -> top_left [style=solid,
			label=<<TABLE BORDER="0"><TR><TD><IMG SRC="images/warning.png"/></TD></TR></TABLE>>,
			dir=back,
			color="#0a879a"];
		bottom_right -> top_right [style=solid,
			label=<<TABLE BORDER="0"><TR><TD><IMG SRC="images/warning.png"/></TD></TR></TABLE>>,
			dir=back,
			color="#0a879a",
			penwidth=5.0];
}
