'Implements the GET method as described in the class docstring.'

def get(self, request, course_id):

    course_key = CourseKey.from_string(course_id)
    topic_ids = self.request.GET.get('topic_id')
    with modulestore().bulk_operations(course_key):
        response = get_course_topics(request, course_key, (set(topic_ids.strip(',').split(',')) if topic_ids else None))
    return Response(response)
