public static <E extends Number> AbstractGroupExpression<E, E> avg(Expression<E> expression) {
        return new GAvg<E>(expression);
    }
Create a new aggregating avg expression, uses default MathContext.DECIMAL128 for average calculation

@param expression expression for which the accumulated average value will be used in the group by projection
@return wrapper expression
querydsl-core/src/main/java/com/querydsl/core/group/GroupBy.java