dev(hansbug): add pop method for TreeValue

test(hansbug): add test for misusage of raw function

dev(hansbug): new feature in getitem, setitem and delitem

dev(hansbug): add getitem, setitem and delitem for adding, editing and removing items in TreeValue class

dev(hansbug): add walk method for FastTreeValue class

dev(hansbug): optimize union

test(hansbug): add compare with facebook nest library

dev(hansbug): add keys, values and items for TreeValue class

dev(hansbug): update the tree print system