chore: Fix types

Author: anubhav756

packages/toolbox-core/src/toolbox_core/sync_client.py

@@ -63,15 +63,15 @@ async def create_client():
         ).result()
 
     @property
-    def _async_client(self) -> Optional[ToolboxClient]:
+    def _async_client(self) -> ToolboxClient:
         return self.__async_client
 
     @property
     def _loop(self) -> Optional[AbstractEventLoop]:
         return self.__class__.__loop
 
     @property
-    def _thread(self) -> Thread:
+    def _thread(self) -> Optional[Thread]:
         return self.__class__.__thread
 
     def close(self):