code: protected String translate(String messageKey, String defaultMessage) {
          if (messages == null || Strings.isNullOrEmpty(messageKey)) {
              return Strings.emptyToNull(defaultMessage);
          }
          return Strings.emptyToNull(messages.getWithDefault(messageKey, defaultMessage, defaultLanguage));
      }
docs: Attempts to provide a localized message.
  
  @param messageKey
  @param defaultMessage
  @return the default message or a localized message or null