'Fetch the course\'s nth grader
Returns an empty dict if there\'s no such grader.'

@staticmethod
def fetch_grader(course_key, index):

    descriptor = modulestore().get_course(course_key)
    index = int(index)
    if (len(descriptor.raw_grader) > index):
        return CourseGradingModel.jsonize_grader(index, descriptor.raw_grader[index])
    else:
        return {'id': index, 'type': '', 'min_count': 0, 'drop_count': 0, 'short_label': None, 'weight': 0}
