@Override
    public ScalarOperator visitIsNullPredicate(IsNullPredicateOperator predicate, Void context) {
        return shuttleIfUpdate(predicate);
    }
@Test
    void visitIsNullPredicate() {
        IsNullPredicateOperator operator = new IsNullPredicateOperator(true, new ColumnRefOperator(1, INT, "id", true));
        {
            ScalarOperator newOperator = shuttle.visitIsNullPredicate(operator, null);
            assertEquals(operator, newOperator);
        }
        {
            ScalarOperator newOperator = shuttle2.visitIsNullPredicate(operator, null);
            assertEquals(operator, newOperator);
        }
    }