How to stream network output using toAISdkFormat(result, { from: "network" }) in v1 beta?

export async function POST(req: Request) {
  const { messages } = await req.json();

  const stream = await weatherAgent.stream(messages, {
    memory: {
      thread: "example-user-id",
      resource: "weather-chat",
    },
  });

  return createUIMessageStreamResponse({
    stream: toAISdkFormat(stream, { from: "agent" }),
  });
}

stream = await agent.network(..
...
... toAISdkFormat(result, { from: "network" }) 
..