code: protected String getExpressionTextForLanguage(DmnExpressionImpl expression, String expressionLanguage) {
      String expressionText = expression.getExpression();
      if (expressionText != null) {
        if (isJuelExpression(expressionLanguage) && !StringUtil.isExpression(expressionText)) {
          return "${" + expressionText + "}";
        } else {
          return expressionText;
        }
      } else {
        return null;
      }
    }
docs: helper ///////////////////////////////////////////////////////////////////