change yroom class attribute to instance attribute

Author: Jialin Zhang

Diff for: pycrdt_websocket/yroom.py

@@ -4,7 +4,7 @@
 from functools import partial
 from inspect import isawaitable
 from logging import Logger, getLogger
-from typing import Awaitable, Callable
+from typing import Awaitable, Callable, Tuple
 
 from anyio import (
     TASK_STATUS_IGNORED,
@@ -37,12 +37,11 @@ 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,
@@ -82,6 +81,13 @@ def __init__(
         self._on_message = None
         self.exception_handler = exception_handler
         self._stopped = Event()
+        self._update_send_stream, self._update_receive_stream = create_memory_object_stream(
+                max_buffer_size=65536
+        )
+        self._task_group = None
+        self._started = None
+        self.__start_lock = None
+        self._subscription= None
 
     @property
     def _start_lock(self) -> Lock: