'Delete the grader of the given type from the given course.'

@staticmethod
def delete_grader(course_key, index, user):

    descriptor = modulestore().get_course(course_key)
    index = int(index)
    if (index < len(descriptor.raw_grader)):
        del descriptor.raw_grader[index]
        descriptor.raw_grader = descriptor.raw_grader
    modulestore().update_item(descriptor, user.id)
    _grading_event_and_signal(course_key, user.id)
