public static <T> List<LocalProperty<T>> sorted(Collection<T> columns, SortOrder order)
    {
        return columns.stream().map(column -> new SortingProperty<>(column, order)).collect(toImmutableList());
    }
@Test
    public void testNormalizeDifferentSorts()
    {
        List<LocalProperty<String>> localProperties = builder()
                .sorted("a", SortOrder.ASC_NULLS_FIRST)
                .sorted("a", SortOrder.DESC_NULLS_LAST)
                .build();
        assertNormalize(
                localProperties,
                Optional.of(sorted("a", SortOrder.ASC_NULLS_FIRST)),
                Optional.empty());
        assertNormalizeAndFlatten(
                localProperties,
                sorted("a", SortOrder.ASC_NULLS_FIRST));
    }