List all the contact channel codes that were used less than 5 times.
SELECT channel_code FROM customer_contact_channels GROUP BY channel_code HAVING count(customer_id)  <  5
SELECT channel_code FROM customer_contact_channels GROUP BY channel_code HAVING count(customer_id)  <  5
[{'channel_code': 'Cell'}, {'channel_code': 'Email'}, {'channel_code': 'Fax'}, {'channel_code': 'Mobile'}]