@Override
  public String validateInputLink(Operator precedingOperator) {
    String message = super.validateInputLink(precedingOperator);
    if (message == null || message.trim().equals("")) {
      if (!(precedingOperator instanceof RandomSamplingOperator)
          && !(precedingOperator instanceof StratifiedSamplingOperator)) {
        message =
            NLSUtility.bind(
                LanguagePack.getMessage(LanguagePack.MESSAGE_CHECK_LINK, locale),
                precedingOperator.getToolTipTypeName(),
                this.getToolTipTypeName());
      }
    }

    if (message == null || message.trim().equals("")) {
      List<UIOperatorModel> parentList = OperatorUtility.getParentList(getOperModel());
      if (parentList != null && parentList.size() > 0) {
        message =
            NLSUtility.bind(
                LanguagePack.getMessage(LanguagePack.CANNOT_LINKMUTIL_TOOPERATOR, locale),
                this.getToolTipTypeName());
      }
    }
    return message;
  }
 @Override
 public String getToolTipTypeName() {
   return LanguagePack.getMessage(LanguagePack.SAMPLE_SELECTOR_OPERATOR, locale);
 }
 @Override
 public String getToolTipTypeName() {
   return LanguagePack.getMessage(LanguagePack.FREQUENCY_OPERATOR, locale);
 }