code: protected Set<String> configureContentTypeSuffixes(ContentTypeEngines engines) {
          if (null == ClassUtil.getAnnotation(method, ContentTypeBySuffix.class)) {
              return Collections.emptySet();
          }
  
          Set<String> suffixes = new TreeSet<>();
          for (String suffix : engines.getContentTypeSuffixes()) {
              String contentType = engines.getContentTypeEngine(suffix).getContentType();
              if (declaredProduces.contains(contentType)) {
                  suffixes.add(suffix);
              }
          }
          return suffixes;
      }
docs: Configures the content-type suffixes
  
  @param engines
  @return acceptable content-type suffixes