public Set<E> getAllEdges(V sourceVertex, V targetVertex) {
Set<E> res = new HashSet<E>();
if (g1.containsVertex(sourceVertex) && g1.containsVertex(targetVertex)) {
res.addAll(g1.getAllEdges(sourceVertex, targetVertex));
}
if (g2.containsVertex(sourceVertex) && g2.containsVertex(targetVertex)) {
res.addAll(g2.getAllEdges(sourceVertex, targetVertex));
}
return Collections.unmodifiableSet(res);
}
