presto-main/src/main/java/io/prestosql/sql/planner/iterative/Lookup.java/Lookup/from
class Lookup:    static Lookup from(Function<GroupReference, Stream<PlanNode>> resolver)
    {
        return node -> {
            checkArgument(node instanceof GroupReference, "Node '%s' is not a GroupReference", node.getClass().getSimpleName());
            return resolver.apply((GroupReference) node);
        };
    }