Allow None return from grpc.aio.ServerInterceptor.intercept_service

Author: Rhadamanthus1

stubs/grpcio/grpc/aio/__init__.pyi

@@ -375,12 +375,15 @@ class ServerInterceptor(metaclass=abc.ABCMeta):
     # This method (not the class) is generic over _TRequest and _TResponse
     # and the types must satisfy the no-op implementation of
     # `return await continuation(handler_call_details)`.
+    # The return is Optional: per the runtime docstring, an interceptor
+    # may return None to signal that the RPC is not serviced, and the
+    # continuation propagates that None down the chain.
     @abc.abstractmethod
     async def intercept_service(
         self,
-        continuation: Callable[[HandlerCallDetails], Awaitable[RpcMethodHandler[_TRequest, _TResponse]]],
+        continuation: Callable[[HandlerCallDetails], Awaitable[RpcMethodHandler[_TRequest, _TResponse] | None]],
         handler_call_details: HandlerCallDetails,
-    ) -> RpcMethodHandler[_TRequest, _TResponse]: ...
+    ) -> RpcMethodHandler[_TRequest, _TResponse] | None: ...
 
 # Multi-Callable Interfaces: