Return the themes of farm competitions, sorted by year ascending.
SELECT Theme FROM farm_competition ORDER BY YEAR ASC
SELECT Theme FROM farm_competition ORDER BY YEAR ASC
[{'Theme': 'Aliens'}, {'Theme': 'MTV Cube'}, {'Theme': "Valentine's Day"}, {'Theme': 'MTV Asia Aid'}, {'Theme': 'Codehunters'}, {'Theme': 'Carnival M is back!'}]