change yroom class attribute to instance attribute

pycrdt_websocket/yroom.py

@@ -37,12 +37,12 @@ class YRoom:
     _on_message: Callable[[bytes], Awaitable[bool] | bool] | None
     _update_send_stream: MemoryObjectSendStream
     _update_receive_stream: MemoryObjectReceiveStream
-    _task_group: TaskGroup | None = None
-    _started: Event | None = None
+    _task_group: TaskGroup | None
+    _started: Event | None
     _stopped: Event
-    __start_lock: Lock | None = None
-    _subscription: Subscription | None = None
-
+    __start_lock: Lock | None
+    _subscription: Subscription | None
+    
     def __init__(
         self,
         ready: bool = True,
@@ -82,7 +82,11 @@ def __init__(
         self._on_message = None
         self.exception_handler = exception_handler
         self._stopped = Event()
-
+        self._task_group = None
+        self._started = None
+        self.__start_lock = None
+        self._subscription = None
+
     @property
     def _start_lock(self) -> Lock:
         if self.__start_lock is None:
@@ -230,6 +234,7 @@ async def stop(self) -> None:
         self._stopped.set()
         self._task_group.cancel_scope.cancel()
         self._task_group = None
+        await self.ystore.stop()
         if self._subscription is not None:
             self.ydoc.unobserve(self._subscription)