code: public static String filterHtmlElementName(String value) {
      if (EscapingConventions.FilterHtmlElementName.INSTANCE.getValueFilter().matcher(value).find()) {
        return value;
      }
      logger.log(Level.WARNING, "|filterHtmlElementName received bad value ''{0}''", value);
      return EscapingConventions.FilterHtmlElementName.INSTANCE.getInnocuousOutput();
    }
docs: Checks that the input is part of the name of an innocuous element.