def METHOD_NAME(cls, course_id):
    """ Retrieve a single course. """
    try:
        course_id = CourseKey.from_string(str(course_id))
    except InvalidKeyError:
        log.debug('[%s] is not a valid course key.', course_id)
        raise ValueError  # lint-amnesty, pylint: disable=raise-missing-from
    course_modes = CourseMode.objects.filter(course_id=course_id)
    if course_modes:
        verification_deadline = VerificationDeadline.deadline_for_course(course_id)
        return cls(course_id, list(course_modes), verification_deadline=verification_deadline)
    return None