presto-main/src/main/java/io/prestosql/sql/planner/optimizations/OptimizeMixedDistinctAggregations.java/OptimizeMixedDistinctAggregations/getGroupBySymbols
class OptimizeMixedDistinctAggregations:        public List<Symbol> getGroupBySymbols()
        {
            return groupBySymbols;
        }