docs: public static Function<String, String> createStringTemplateSource(
          I_CmsFormatterBean formatter,
          Supplier<CmsXmlContent> contentSupplier) {
  
          return key -> {
              String result = null;
              if (formatter != null) {
                  result = formatter.getAttributes().get(key);
              }
              if (result == null) {
                  CmsXmlContent content = contentSupplier.get();
                  if (content != null) {
                      result = content.getHandler().getParameter(key);
                  }
              }
              return result;
          };
      }