presto-main/src/main/java/io/prestosql/sql/planner/optimizations/PlanNodeSearcher.java/PlanNodeSearcher/PlanNodeSearcher
class PlanNodeSearcher:    private PlanNodeSearcher(PlanNode node, Lookup lookup)
    {
        this.node = requireNonNull(node, "node is null");
        this.lookup = requireNonNull(lookup, "lookup is null");
    }