remove unused code

lib/backend.py

@@ -91,17 +91,6 @@ class Backend:
         timeout = ClientTimeout(total=None)
         return ClientSession(self.model_server_url, timeout=timeout, connector=connector)
 
-    async def _worker(self):
-        while True:
-            handler, request, fut = await self.request_queue.get()
-            try:
-                res = await self.__process_request(handler, request)
-                fut.set_result(res)
-            except Exception as e:
-                fut.set_exception(e)
-            finally:
-                self.request_queue.task_done()
-
     def create_handler(
         self,
         handler: EndpointHandler[ApiPayload_T],