Before reading - Wait, how they are going to modernise something that is working well? What do they mean by modernise? Is the modernise technique really bett

Before reading - Wait, how they are going to modernise something that is working well? What do they mean by modernise? Is the modernise technique really better ? First read - There is really no modernisation done and no improvements at all until I saw the chart. Second read - Very carefully trying to understand and found that they removed legacy technique to access a node and replaced it with a node with four pointers - parent, first-child, next, and previous sibling. Its a neat work because trying to migrate a older technique to newer ones will require deeper knowledge !