public static <E> AbstractGroupExpression<E, Set<E>> set(Expression<E> expression) {
        return GSet.createLinked(expression);
    }
Create a new aggregating set expression using a backing LinkedHashSet

@param expression values for this expression will be accumulated into a set
@return wrapper expression
querydsl-core/src/main/java/com/querydsl/core/group/GroupBy.java