docs: String getResourceTypeFilter() {
  
          String result = "";
          List<String> typeVals = Lists.newArrayList();
          if (!m_config.getDisplayTypes().isEmpty()) {
              for (String displayType : m_config.getDisplayTypes()) {
                  if (displayType.contains(CmsXmlDisplayFormatterValue.SEPARATOR)) {
                      displayType = displayType.substring(0, displayType.indexOf(CmsXmlDisplayFormatterValue.SEPARATOR));
                  }
                  typeVals.add("\"" + displayType + "\"");
              }
          }
          if (!typeVals.isEmpty()) {
              result = "&fq=type:(" + CmsStringUtil.listAsString(typeVals, " OR ") + ")";
          }
          return result;
      }