presto-parser/src/main/java/io/prestosql/sql/tree/ExistsPredicate.java/ExistsPredicate/ExistsPredicate
class ExistsPredicate:    private ExistsPredicate(Optional<NodeLocation> location, Expression subquery)
    {
        super(location);
        requireNonNull(subquery, "subquery is null");
        this.subquery = subquery;
    }