@Override
    public String toString() {
        if (str == null)
            str = attributeSelector.toStringBuilder()
                    .append("/Value[@number=\"")
                    .append(valueIndex + 1)
                    .append("\"]")
                    .toString();
        return str;
    }
@Test
    public void testToString() {
        ItemPointer ip = new ItemPointer(Tag.RequestAttributesSequence, 0);
        ValueSelector vs = new ValueSelector(Tag.StudyInstanceUID, null, 0, ip);
        assertEquals(XPATH, vs.toString());
    }