- isEmpty (check if BST is empty)
- addBST (add data to BST)
- removeBST (remove data from BST)
- searchBST (check if the key exists in BST)
- isEmpty (check if BST is empty)
- addBST (add data to BST)
- removeBST (remove data from BST)
- searchBST (check if the key exists in BST)