Could i set the Side_data such as sei using the pyav?

[Pure0319]

I know i can get the sidedata from the code

if packet.stream.type == 'video':
        for frame in packet.decode():
            print(frame.side_data.get("SEI_UNREGISTERED"))

but i want to konw if i can set the SEI_UNREGISTERED of every frame?
thanks