'Retrieve the verification deadline for a particular course.
Arguments:
course_key (CourseKey): The identifier for the course.
Returns:
datetime or None'

@classmethod
def deadline_for_course(cls, course_key):

    try:
        deadline = cls.objects.get(course_key=course_key)
        return deadline.deadline
    except cls.DoesNotExist:
        return None
