code: @Override
      public ContentSerializer getBestSerializer(Collection<MediaType> mediaTypes) {
          if (mediaTypes == null  || mediaTypes.isEmpty()) {
              mediaTypes = ImmutableList.of(MediaType.HTML_UTF_8);
          }
          for (MediaType type : mediaTypes) {
              for (ContentSerializer ser : serializers) {
                  MediaType mt = MediaType.parse(ser.getContentType());
                  if (mt.is(type.withoutParameters())) {
                      return ser;
                  }
              }
          }
          return null;
      }
docs: Finds the 'best' content serializer for the given accept headers.
  
  @param mediaTypes the ordered set of {@link com.google.common.net.MediaType} from the {@code ACCEPT} header.
  @return the best serializer from the list matching the {@code ACCEPT} header, {@code null} if none match