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

docs_src/additional_responses/tutorial003_py39.py

@@ -0,0 +1,37 @@
+from fastapi import FastAPI
+from fastapi.responses import JSONResponse
+from pydantic import BaseModel
+
+
+class Item(BaseModel):
+    id: str
+    value: str
+
+
+class Message(BaseModel):
+    message: str
+
+
+app = FastAPI()
+
+
+@app.get(
+    "/items/{item_id}",
+    response_model=Item,
+    responses={
+        404: {"model": Message, "description": "The item was not found"},
+        200: {
+            "description": "Item requested by ID",
+            "content": {
+                "application/json": {
+                    "example": {"id": "bar", "value": "The bar tenders"}
+                }
+            },
+        },
+    },
+)
+async def read_item(item_id: str):
+    if item_id == "foo":
+        return {"id": "foo", "value": "there goes my hero"}
+    else:
+        return JSONResponse(status_code=404, content={"message": "Item not found"})