Sync fastapi docs from 50fa3f7c on 2026-01-11

docs_src/query_params/tutorial002_py39.py

@@ -0,0 +1,12 @@
+from typing import Union
+
+from fastapi import FastAPI
+
+app = FastAPI()
+
+
+@app.get("/items/{item_id}")
+async def read_item(item_id: str, q: Union[str, None] = None):
+    if q:
+        return {"item_id": item_id, "q": q}
+    return {"item_id": item_id}