static Multimap<String, Range<Integer>> extractHighlightRanges(Map<String, List<String>> highlight) {
        if (highlight == null || highlight.isEmpty()) {
            return ImmutableListMultimap.of();
        }
        final ImmutableListMultimap.Builder<String, Range<Integer>> builder = ImmutableListMultimap.builder();
        highlight.forEach((key, value) -> extractRange(value).forEach(range -> builder.put(key, range)));
        return builder.build();
    }
@Test
    public void nullHighlights() throws Exception {
        final Multimap<String, Range<Integer>> result = HighlightParser.extractHighlightRanges(null);

        assertThat(result).isNotNull();
        assertThat(result.entries()).isEmpty();
    }