/* Add a todolist
    acceptation criterias:
    - the todolist is present in the list of todolists
*/

/* Delete a todolist
    acceptation criterias:
    - all the subsequent todos must be deleted
*/

/* List all todolists
    acceptation criteria:
    - returns all todolists
*/

/* Add a todo to a list
    acceptation criteria:
    - the todo is present in the todolist
    - the todolist doesn't have to be ordered
*/

/* Delete a todo to a list
    acceptation criteria:
    - the todo is not present in the todolist anymore but the others are
*/

/* List todos of a list
    acceptation criteria:
    - all todos of this todolist must be present and not the other todos from the other todolists
*/