presto-main/src/main/java/io/prestosql/sql/planner/optimizations/HashGenerationOptimizer.java/HashGenerationOptimizer/PlanWithProperties
class HashGenerationOptimizer:        public PlanWithProperties(PlanNode node, Map<HashComputation, Symbol> hashSymbols)
        {
            this.node = requireNonNull(node, "node is null");
            this.hashSymbols = ImmutableBiMap.copyOf(requireNonNull(hashSymbols, "hashSymbols is null"));
        }