presto-main/src/main/java/io/prestosql/sql/analyzer/FeaturesConfig.java/FeaturesConfig/setMultimapAggGroupImplementation
class FeaturesConfig:    @Config("multimapagg.implementation")
    public FeaturesConfig setMultimapAggGroupImplementation(MultimapAggGroupImplementation groupByMode)
    {
        this.multimapAggGroupImplementation = groupByMode;
        return this;
    }