private Edge? GetEdgeToExtend(Graph g, Edge e)
{
foreach (var e2 in NonplanarSubgraph.GetAllEdges())
{
if (!g.ContainsEdge(e2.U, e2.V) && g.ContainsEdge(e.V, e2.U) && g.ContainsEdge(e.V, e2.V))
{
return e2;
}
}
return null;
}
