public String toString() {
IndexMap<Node> map = new IndexMap<Node>(numNodes());
String s = "";
for (Node node : getNodes()) s += "Node " + map.set(node) + ": " + node + "\n";
s += "Roots: ";
for (Node node : getRoots()) s += map.get(node) + " ";
s += "\nEdges:\n";
for (Node node : getNodes()) {
int i = map.get(node);
for (Node node2 : getSuccs(node)) s += i + " -> " + map.get(node2) + "\n";
}
return s;
}