private static BinarySearchTree ConstructSampleBSTWithParentPointer()
{
var tree = new BinarySearchTree();
tree.InsertWithParentPointerUpdated(5);
tree.InsertWithParentPointerUpdated(3);
tree.InsertWithParentPointerUpdated(1);
tree.InsertWithParentPointerUpdated(4);
tree.InsertWithParentPointerUpdated(6);
return tree;
}