private static void InsertAntecedent(List <AbstractMaterialNode> nodes, AbstractMaterialNode node)
{
var upstream = node.GetInputSlots <MaterialSlot>().Where(slot => slot.isConnected).Select(slot => node.GetInputNodeFromSlot(slot.id));
int safeIdx = nodes.FindLastIndex(n => upstream.Contains(n)) + 1;
nodes.Insert(safeIdx, node);
}