protected boolean isIpPrefix(String field, FieldPresence presence) {
        return isIpPrefix(object, field, presence);
    }
@Test
    public void isIpPrefix() {
        assertTrue("is not proper prefix", cfg.isIpPrefix(PREFIX, MANDATORY));
        assertTrue("is not proper prefix", cfg.isIpPrefix(PREFIX, OPTIONAL));
        assertTrue("is not proper prefix", cfg.isIpPrefix("none", OPTIONAL));
        assertTrue("did not detect missing prefix",
                expectInvalidField(() -> cfg.isIpPrefix("none", MANDATORY)));
        assertTrue("did not detect bad prefix",
                expectInvalidField(() -> cfg.isIpPrefix(BAD_PREFIX, MANDATORY)));
    }