presto-main/src/main/java/io/prestosql/sql/planner/plan/AggregationNode.java/AggregationNode/groupingSets
class AggregationNode:    public static GroupingSetDescriptor groupingSets(List<Symbol> groupingKeys, int groupingSetCount, Set<Integer> globalGroupingSets)
    {
        return new GroupingSetDescriptor(groupingKeys, groupingSetCount, globalGroupingSets);
    }