Fix CI failures for python 3.9

Author: 3coins

jupyter_rtc_core/websockets/clients.py

@@ -7,7 +7,7 @@
 from __future__ import annotations
 from datetime import timedelta, timezone, datetime
 from logging import Logger
-from typing import TYPE_CHECKING
+from typing import Optional, TYPE_CHECKING
 import uuid
 import asyncio
 
@@ -91,7 +91,7 @@ def __init__(self, *, room_id: str, log: Logger, loop: asyncio.AbstractEventLoop
         self.desynced_timeout_seconds = desynced_timeout_seconds
         self._stopped = False
 
-    def add(self, websocket: WebSocketHandler) -> str | None:
+    def add(self, websocket: WebSocketHandler) -> Optional[str]:
         """
         Adds a new Websocket as a client to the group.
 

jupyter_rtc_core/websockets/yroom_ws.py

@@ -1,7 +1,7 @@
 from __future__ import annotations
 from tornado.httpclient import HTTPError
 from tornado.websocket import WebSocketHandler
-from typing import TYPE_CHECKING
+from typing import Optional, TYPE_CHECKING
 import asyncio
 from ..rooms import YRoomManager
 import logging
@@ -14,7 +14,7 @@
 class YRoomWebsocket(WebSocketHandler):
     yroom: YRoom
     room_id: str
-    client_id: str | None
+    client_id: Optional[str]
     # TODO: change this. we should pass `self.log` from our
     # `ExtensionApp` to log messages w/ "RtcCoreExtension" prefix
     log = logging.Logger("TEMP")