AttributeError: module 'av' has no attribute 'AV_FRAME_DATA_SEI_UNREGISTERED'

Created by: lzou

import av

def frame_iter(video):
    #streams = [s for s in video.streams if s.type == b'video']
    #print(streams)
    streams = video.streams.video
    for packet in video.demux(streams):
        # print(packet, packet.buffer_size, packet.buffer_ptr,dir(packet))
        for frame in packet.decode():
            yield frame

if __name__ == '__main__':
    url='/Users/zoulu/Downloads/date.mp4'

    video = av.open(url)
    # print(video, video.streams.video)

    frames = frame_iter(video)
    for frame in frames:
        sei = frame.side_data.get(av.AV_FRAME_DATA_SEI_UNREGISTERED)
        print(sei.data) 

when i run the code. it tell me

Traceback (most recent call last): File "/Users/zoulu/sei.py", line 20, in <module> sei = frame.side_data.get(av.AV_FRAME_DATA_SEI_UNREGISTERED) AttributeError: module 'av' has no attribute 'AV_FRAME_DATA_SEI_UNREGISTERED'