presto-main/src/main/java/io/prestosql/operator/TopNOperator.java/TopNOperatorFactory/TopNOperatorFactory
class TopNOperatorFactory:        public TopNOperatorFactory(
                int operatorId,
                PlanNodeId planNodeId,
                List<? extends Type> types,
                int n,
                List<Integer> sortChannels,
                List<SortOrder> sortOrders)
        {
            this.operatorId = operatorId;
            this.planNodeId = requireNonNull(planNodeId, "planNodeId is null");
            this.sourceTypes = ImmutableList.copyOf(requireNonNull(types, "types is null"));
            this.n = n;
            this.sortChannels = ImmutableList.copyOf(requireNonNull(sortChannels, "sortChannels is null"));
            this.sortOrders = ImmutableList.copyOf(requireNonNull(sortOrders, "sortOrders is null"));
        }