Fix type error in blackd

src/blackd/middlewares.py

@@ -3,20 +3,26 @@
 from aiohttp.web_request import Request
 from aiohttp.web_response import StreamResponse
 
+Handler = Callable[[Request], Awaitable[StreamResponse]]
+
 if TYPE_CHECKING:
+    from aiohttp.typedefs import Middleware
+
     F = TypeVar("F", bound=Callable[..., Any])
     middleware: Callable[[F], F]
 else:
+    try:
+        from aiohttp.typedefs import Middleware
+    except ImportError:
+        Middleware = Callable[[Request, Handler], Awaitable[StreamResponse]]
+
     try:
         from aiohttp.web_middlewares import middleware
     except ImportError:
         # @middleware is deprecated and its behaviour is the default since aiohttp 4.0
         # so if it doesn't exist anymore, define a no-op for forward compatibility.
         middleware = lambda x: x  # noqa: E731
 
-Handler = Callable[[Request], Awaitable[StreamResponse]]
-Middleware = Callable[[Request, Handler], Awaitable[StreamResponse]]
-
 
 def cors(allow_headers: Iterable[str]) -> Middleware:
     @middleware