protected int getIndex(Graph<V, E> graph, E e, V v) {
Collection<E> commonEdgeSet = new HashSet<E>();
for (E another : graph.getIncidentEdges(v)) {
V u = graph.getOpposite(v, another);
if (u.equals(v)) {
commonEdgeSet.add(another);
}
}
int count = 0;
for (E other : commonEdgeSet) {
if (e.equals(other) == false) {
edge_index.put(other, count);
count++;
}
}
edge_index.put(e, count);
return count;
}