'Create a set of example certificates for a course.
Arguments:
course_key (CourseKey)
Returns:
ExampleCertificateSet'

@classmethod
@transaction.atomic
def create_example_set(cls, course_key):

    from course_modes.models import CourseMode
    cert_set = cls.objects.create(course_key=course_key)
    ExampleCertificate.objects.bulk_create([ExampleCertificate(example_cert_set=cert_set, description=mode.slug, template=cls._template_for_mode(mode.slug, course_key)) for mode in CourseMode.modes_for_course(course_key)])
    return cert_set
