@classmethod
def get_allowance_for_user(cls, exam_id, user_id, key):
    """
        Returns an allowance for a user within a given exam
        """
    try:
        student_allowance = cls.objects.get(proctored_exam_id=exam_id,
            user_id=user_id, key=key)
    except cls.DoesNotExist:
        student_allowance = None
    return student_allowance
