| id,user_id,key,value | |
| 1,534,difficulty_estimator,fk | |
| 2,1143,difficulty_estimator,fk | |
| 3,1140,difficulty_estimator,fk | |
| 4,9,difficulty_estimator,fk | |
| 5,534,de_ordering,easiest_first | |
| 6,534,nl_ordering,easiest_first | |
| 7,534,es_ordering,easiest_first | |
| 8,9,es_ordering,easiest_first | |