Find the policy types more than 4 customers use. Show their type code.
SELECT policy_type_code FROM available_policies GROUP BY policy_type_code HAVING count(*)  >  4
SELECT policy_type_code FROM available_policies GROUP BY policy_type_code HAVING count(*)  >  4
[{'policy_type_code': 'Mortgage Insurance'}, {'policy_type_code': 'Property Insurance'}]