Park Dietz was credited in which role in the episode titled "Cherished"?
credited refers to credited = 'true'; titled "Cherished" refers to title = 'Cherished'
SELECT T2.role FROM Episode AS T1 INNER JOIN Credit AS T2 ON T1.episode_id = T2.episode_id INNER JOIN Person AS T3 ON T3.person_id = T2.person_id WHERE T1.title = 'Cherished' AND T3.name = 'Park Dietz' AND T2.credited = 'true'