private void CallMakePretty()
 {
     
     Tree tree = new Tree(selectedNodes,Lines);
     Tree wholeTree = new Tree(tree.getWholeTree(),Lines);
     if (wholeTree.allNodesOneParentAndLessThanThreeChildren())
         undoRedo.InsertInUndoRedo(new MakePrettyCommand(Nodes, selectedNodes));
 }