use BinaryTreeTraversals (Tree, integer);

BT = Tree(
	Tree(
          Tree(Leaf(7), 4, null(Tree)), 2 , Leaf(5)), 1,
            Tree(
              Tree(Leaf(8), 6, Leaf(9)), 3 ,null(Tree)));

{Item(Preorder(BT))}?
{ 1, 2, 4, 7, 5, 3, 6, 8, 9}

{Item(Inorder(BT))}?
{ 7, 4, 2, 5, 1, 8, 6, 9, 3}

{Item(Postorder(BT))}?
{ 7, 4, 5, 2, 8, 9, 6, 3, 1}

{Item(Level_order(BT))}?
{ 1, 2, 3, 4, 5, 6, 7, 8, 9}