@Override
    public void setSortKeys(List<? extends SortKey> keys) {
        switch (keys.size()) {
            case 0:
                setSortKey(null);
                break;
            case 1:
                setSortKey(keys.get(0));
                break;
            default:
                throw new IllegalArgumentException("Only one column can be sorted");
        }
    }
@Test
    public void setSortKeys_invalidColumn() {
        assertThrows(
                IllegalArgumentException.class,
                () -> sorter.setSortKeys(Collections.singletonList(new SortKey(2, SortOrder.ASCENDING))));
    }