public Node parse() throws ScanException {
        if (tokenList == null || tokenList.isEmpty())
            return null;
        return E();
    }
@Test
    public void withColon() throws ScanException {
        Tokenizer tokenizer = new Tokenizer("a:${b}");
        Parser parser = new Parser(tokenizer.tokenize());
        Node node = parser.parse();
        Node witness = new Node(Node.Type.LITERAL, "a");
        Node t = witness.next = new Node(Node.Type.LITERAL, ":");
        t.next = new Node(Node.Type.VARIABLE, new Node(Node.Type.LITERAL, "b"));
        assertEquals(witness, node);
    }