presto-main/src/main/java/io/prestosql/operator/aggregation/state/QuantileDigestStateFactory.java/GroupedQuantileDigestState/setQuantileDigest
class GroupedQuantileDigestState:        @Override
        public void setQuantileDigest(QuantileDigest value)
        {
            requireNonNull(value, "value is null");
            qdigests.set(getGroupId(), value);
        }