public OrderedProperties filter(Predicate<String> filter) {
        for (Iterator<Entry<String, String>> it = pairs.entrySet().iterator(); it.hasNext(); ) {
            if (filter.test(it.next().getKey())) {
                it.remove();
            }
        }
        return this;
    }
@Test
    public void filter() {
        OrderedProperties pairs = createTestKeyValues();
        pairs.filter(k -> k.equalsIgnoreCase("second"));
        assertKeyOrder(pairs, "first", "third", "FOURTH");
    }