chore: import upstream snapshot with attribution

doc/source/serve/doc_code/http_guide/websockets_example.py

@@ -0,0 +1,39 @@
+# flake8: noqa
+
+# __websocket_serve_app_start__
+from fastapi import FastAPI, WebSocket, WebSocketDisconnect
+
+from ray import serve
+
+
+app = FastAPI()
+
+
+@serve.deployment
+@serve.ingress(app)
+class EchoServer:
+    @app.websocket("/")
+    async def echo(self, ws: WebSocket):
+        await ws.accept()
+
+        try:
+            while True:
+                text = await ws.receive_text()
+                await ws.send_text(text)
+        except WebSocketDisconnect:
+            print("Client disconnected.")
+
+
+serve_app = serve.run(EchoServer.bind())
+# __websocket_serve_app_end__
+
+# __websocket_serve_client_start__
+from websockets.sync.client import connect
+
+with connect("ws://localhost:8000") as websocket:
+    websocket.send("Eureka!")
+    assert websocket.recv() == "Eureka!"
+
+    websocket.send("I've found it!")
+    assert websocket.recv() == "I've found it!"
+# __websocket_serve_client_end__