presto-main/src/main/java/io/prestosql/operator/aggregation/state/HyperLogLogStateSerializer.java/HyperLogLogStateSerializer/serialize
class HyperLogLogStateSerializer:    @Override
    public void serialize(HyperLogLogState state, BlockBuilder out)
    {
        if (state.getHyperLogLog() == null) {
            out.appendNull();
        }
        else {
            HYPER_LOG_LOG.writeSlice(out, state.getHyperLogLog().serialize());
        }
    }