presto-main/src/main/java/io/prestosql/cost/PlanNodeStatsEstimate.java/PlanNodeStatsEstimate/toString
class PlanNodeStatsEstimate:    @Override
    public String toString()
    {
        return toStringHelper(this)
                .add("outputRowCount", outputRowCount)
                .add("symbolStatistics", symbolStatistics)
                .toString();
    }