@Override
    public String toString() {
        return prettyString.get();
    }
@Test
    public void testToString() {
        String input = "<root>   <a some='foo '/><b attr='4' ><c>42</c></b></root>";
        CharSequence xml = XmlString.prettifyXml(input);
        String expected = "<root>\n"
                        + "  <a some=\"foo \"/>\n"
                        + "  <b attr=\"4\">\n"
                        + "    <c>42</c>\n"
                        + "  </b>\n"
                        + "</root>\n";
        assertEquals(expected, xml.toString());
    }