protected static String joinCreators(List<String> creators) {
        if (creators == null || creators.size() == 0) {
            return "";
        }
        if (creators.size() == 1) {
            return creators.get(0);
        }
        StringJoiner stringJoiner = new StringJoiner(", ");
        for (String s : creators) {
            stringJoiner.add(s);
        }
        return stringJoiner.toString();
    }
@Test
    public void testJoinCreators() {
        assertEquals("Mr B", new JempboxExtractor(null).joinCreators(Collections.singletonList("Mr B")));
        // TODO use multi-value property instead?
        assertEquals("Mr B, Mr A",
                new JempboxExtractor(null).joinCreators(Arrays.asList("Mr B", "Mr A")));
    }