void addMulti(String name, Collection<String> values) {
        if (!values.isEmpty()) {
            filters.put("Filter." + index + ".Name", name);
            int valueIndex = 1;
            for (String value : values) {
                filters.put(String.format("Filter.%d.Value.%d", index, valueIndex++), value);
            }
            ++index;
        }
    }
@Test
    public void addMulti() {
        // given
        Filter filter = new Filter();

        // when
        filter.addMulti("key", asList("value", "second-value"));

        // then
        Map<String, String> result = filter.getFilterAttributes();

        // then
        assertEquals(3, result.size());
        assertEquals("key", result.get("Filter.1.Name"));
        assertEquals("value", result.get("Filter.1.Value.1"));
        assertEquals("second-value", result.get("Filter.1.Value.2"));
    }