@Override
    public ScalarOperator visitCall(CallOperator call, Void context) {
        return shuttleIfUpdate(call);
    }
@Test
    void testCallOperator() {
        CallOperator operator = new CallOperator("count", INT, Lists.newArrayList());
        {
            ScalarOperator newOperator = shuttle.visitCall(operator, null);
            assertEquals(operator, newOperator);
        }
        {
            ScalarOperator newOperator = shuttle2.visitCall(operator, null);
            assertEquals(operator, newOperator);
        }
    }