'Summarize the latest status of example certificates for a course.
Arguments:
course_key (CourseKey)
Returns:
list: List of status dictionaries.  If no example certificates
have been started yet, returns None.'

@classmethod
def latest_status(cls, course_key):

    try:
        latest = cls.objects.filter(course_key=course_key).latest()
    except cls.DoesNotExist:
        return None
    queryset = ExampleCertificate.objects.filter(example_cert_set=latest).order_by('-created')
    return [cert.status_dict for cert in queryset]
