How many kinds of violations did "Stacks Restaurant" have on 2016/10/4?
"Stacks Restaurant" is the name of the business; date = '2016-10-04';
SELECT COUNT(DISTINCT T1.violation_type_id) FROM violations AS T1 INNER JOIN businesses AS T2 ON T1.business_id = T2.business_id WHERE T2.name = 'Stacks Restaurant' AND T1.`date` = '2016-10-04'