presto-main/src/main/java/io/prestosql/operator/StreamingAggregationOperator.java/StreamingAggregationOperator/toTypes
class StreamingAggregationOperator:    private static List<Type> toTypes(List<Type> groupByTypes, List<Aggregator> aggregates)
    {
        ImmutableList.Builder<Type> builder = ImmutableList.builder();
        builder.addAll(groupByTypes);
        aggregates.stream()
                .map(Aggregator::getType)
                .forEach(builder::add);
        return builder.build();
    }