code: public static <T> WindowOver<T> ratioToReport(Expression<T> expr) {
          return new WindowOver<T>(expr.getType(), SQLOps.RATIOTOREPORT, expr);
      }
docs: computes the ratio of a value to the sum of a set of values. If expr evaluates to null,
  then the ratio-to-report value also evaluates to null.
  
  @return ratio_to_report(expr)