List the authors who created review for podcast titled 'Pop Rocket' in 2016 with rating less than 5.
Pop Rocket' is the title of podcast; in 2016 refers to created_at like'2016%'; rating less than 5 refers to rating < 5; author refers to author_id
SELECT T2.author_id FROM podcasts AS T1 INNER JOIN reviews AS T2 ON T2.podcast_id = T1.podcast_id WHERE T1.title = 'Pop Rocket' AND T2.created_at LIKE '2016-%' AND T2.rating < 5
database name:db_id music_platform_2
runs table runs Cols: run at dtype text, max row id dtype integer, reviews added dtype integer, 
podcasts table podcasts Cols: podcast id dtype text, itunes id dtype integer, slug dtype text, itunes url dtype text, title dtype text, 
reviews table reviews Cols: podcast id dtype text, title dtype text, content dtype text, rating dtype integer, author id dtype text, created at dtype text, 
categories table categories Cols: podcast id dtype text, category dtype text, 
