presto-main/src/main/java/io/prestosql/sql/planner/plan/Patterns.java/SemiJoin/getFilteringSource
class SemiJoin:        public static Property<SemiJoinNode, Lookup, PlanNode> getFilteringSource()
        {
            return property(
                    "filteringSource",
                    (SemiJoinNode semiJoin, Lookup lookup) -> lookup.resolve(semiJoin.getFilteringSource()));
        }