'Returns the enrollment mode for the given user for the given course
`user` is a Django User object
`course_id` is our usual course_id string (e.g. "edX/Test101/2013_Fall)
Returns (mode, is_active) where mode is the enrollment mode of the student
and is_active is whether the enrollment is active.
Returns (None, None) if the courseenrollment record does not exist.'

@classmethod
def enrollment_mode_for_user(cls, user, course_id):

    enrollment_state = cls._get_enrollment_state(user, course_id)
    return (enrollment_state.mode, enrollment_state.is_active)
