presto-main/src/main/java/io/prestosql/operator/aggregation/CentralMomentsAggregation.java/CentralMomentsAggregation/combine
class CentralMomentsAggregation:    @CombineFunction
    public static void combine(@AggregationState CentralMomentsState state, @AggregationState CentralMomentsState otherState)
    {
        mergeCentralMomentsState(state, otherState);
    }