presto-main/src/main/java/io/prestosql/cost/PlanNodeStatsEstimate.java/PlanNodeStatsEstimate/getSymbolStatistics
class PlanNodeStatsEstimate:    public SymbolStatsEstimate getSymbolStatistics(Symbol symbol)
    {
        return symbolStatistics.getOrDefault(symbol, SymbolStatsEstimate.unknown());
    }