Fix test setup and ensure stream_item_type is preserved after include_router

tests/test_sse.py

@@ -1,6 +1,6 @@
 import asyncio
 import time
-from collections.abc import AsyncIterable, Iterable
+from collections.abc import AsyncIterable, Iterable, AsyncIterator
 
 import fastapi.routing
 import pytest
@@ -269,7 +269,7 @@ def test_include_router_copies_stream_item_type():
     sub_router = APIRouter()
 
     @sub_router.get("/stream_item_type", response_class=EventSourceResponse)
-    async def stream_item_type_route() -> AsyncIterable[Item]:
+    async def stream_item_type_route() -> AsyncIterator[Item]:
         yield items[0]
 
     assert getattr(sub_router.routes[-1], "stream_item_type", None) == Item