Return the party email that has used party services the greatest number of times.
SELECT t1.party_email FROM parties AS t1 JOIN party_services AS t2 ON t1.party_id  =  t2.customer_id GROUP BY t1.party_email ORDER BY count(*) DESC LIMIT 1
SELECT t1.party_email FROM parties AS t1 JOIN party_services AS t2 ON t1.party_id  =  t2.customer_id GROUP BY t1.party_email ORDER BY count(*) DESC LIMIT 1
[{'party_email': 'frida57@example.org'}]