private void renderHitAttributes(XMLWriter writer, Hit hit) {
        writer.attribute(TYPE, hit.types().stream().collect(Collectors.joining(" ")));
        if (hit.getRelevance() != null)
            writer.attribute(RELEVANCY, hit.getRelevance().toString());
        writer.attribute(SOURCE, hit.getSource());
    }
Creates an XML renderer using a custom executor.
Using a custom executor is useful for tests to avoid creating new threads for each renderer registry.
container-search/src/main/java/com/yahoo/search/rendering/XmlRenderer.java