What is the most common amenity in the dorms?
SELECT T1.amenity_name FROM dorm_amenity AS T1 JOIN has_amenity AS T2 ON T1.amenid  =  T2.amenid GROUP BY T2.amenid ORDER BY count(*) DESC LIMIT 1
SELECT T1.amenity_name FROM dorm_amenity AS T1 JOIN has_amenity AS T2 ON T1.amenid  =  T2.amenid GROUP BY T2.amenid ORDER BY count(*) DESC LIMIT 1
[{'amenity_name': 'Roof'}]