internal void UnpinNodeFromMaxLayer(Node node)
 {
     MaxLayerOfGeomGraph.Remove(node);
 }
 /// <summary>
 /// pins a node to max layer
 /// </summary>
 /// <param name="node"></param>
 internal void PinNodeToMaxLayer(Node node)
 {
     MaxLayerOfGeomGraph.Insert(node);
 }