def remove(self, objective_id, student_id, tutor_id, by_user):
"""Remove an objective from a users set of adopted objectives.
:param objective_id: is the id of the `Objective` to be removed.
:param student_id: is the id of the `User` for whom the `Objective` is being removed.
:param tutor_id: is the id of the `User` who is removing the `Objective`.
:param by_user: is the `User` who is calling the action.
"""
remove_schema = {'id': s.Use(int),
'student_id': s.Use(int),
'tutor_id': s.Use(int)
}
s.Schema(remove_schema).validate({'id': objective_id,
'student_id': student_id,
'tutor_id': tutor_id})
self._check_user_id_or_admin(tutor_id, by_user)
UserObjective.ignore_or_delete(student_id, tutor_id, objective_id)
