We can simplify parts of our LinkedBinaryTree implementation if we make use of of a single sentinel node, referenced as the_sentinel member of the tree instance, such that the sentinel is the parent...

We can simplify parts of our LinkedBinaryTree implementation if we

make use of of a single sentinel node, referenced as the_sentinel member

of the tree instance, such that the sentinel is the parent of the real root of

the tree, and the root is referenced as the left child of the sentinel. Furthermore,

the sentinel will take the place of None as the value of the _left

or _right member for a node without such a child. Give a new implementation

of the update methods _delete and _attach, assuming such a

representation.