color: var(--color-text);
    /* font-size: 18px; */
    font-size: 15px;
    /* font-family: 'Fira Mono', Consolas, Menlo, Monaco, 'Courier New', Courier, monospace; */
    font-family: 'Roboto Mono', 'Fira Mono', Consolas, Menlo, Monaco, 'Courier New', Courier, monospace;
    border-radius: 4px;
    padding: 75px 45px 35px;
    position: relative;
    -webkit-box-sizing: border-box;
            box-sizing: border-box;

```Python hl_lines="35"
{!../../../docs_src/openapi_callbacks/tutorial001.py!}
```

!!! tip
    Notice that you are not passing the router itself (`invoices_callback_router`) to `callback=`, but the attribute `.routes`, as in `invoices_callback_router.routes`.

### Check the docs

@router.get("/router-depends/")
async def router_depends(commons: dict = Depends(common_parameters)):
    return {"in": "router-depends", "params": commons}


@router.get("/router-decorator-depends/", dependencies=[Depends(common_parameters)])
async def router_decorator_depends():
    return {"in": "router-decorator-depends"}


app.include_router(router)

client = TestClient(app)

func StartHealthServer() (installReady *atomic.Value, watchReady *atomic.Value) {
	router := http.NewServeMux()
	installReady, watchReady = initRouter(router)

	go func() {
		_ = http.ListenAndServe(":"+constants.ReadinessPort, router)
	}()

	return
}

func initRouter(router *http.ServeMux) (installReady *atomic.Value, watchReady *atomic.Value) {
	installReady = &atomic.Value{}

We are importing the submodule `items` directly, instead of importing just its variable `router`.

This is because we also have another variable named `router` in the submodule `users`.

If we had imported one after the other, like:

```Python
from .routers.items import router
from .routers.users import router
```

### ❎ 📛 💥

👥 🏭 🔁 `items` 🔗, ↩️ 🏭 🚮 🔢 `router`.

👉 ↩️ 👥 ✔️ ➕1️⃣ 🔢 📛 `router` 🔁 `users`.

🚥 👥 ✔️ 🗄 1️⃣ ⏮️ 🎏, 💖:

```Python
from .routers.items import router
from .routers.users import router
```

`router` ⚪️➡️ `users` 🔜 📁 1️⃣ ⚪️➡️ `items` & 👥 🚫🔜 💪 ⚙️ 👫 🎏 🕰.

, 💪 ⚙️ 👯‍♂️ 👫 🎏 📁, 👥 🗄 🔁 🔗:

### 避免名称冲突

我们将直接导入 `items` 子模块，而不是仅导入其 `router` 变量。

这是因为我们在 `users` 子模块中也有另一个名为 `router` 的变量。

如果我们一个接一个地导入，例如：

```Python
from .routers.items import router
from .routers.users import router
```

来自 `users` 的 `router` 将覆盖来自 `items` 中的 `router`，我们将无法同时使用它们。

因此，为了能够在同一个文件中使用它们，我们直接导入子模块：

```Python hl_lines="5" title="app/main.py"

You can import the `APIRouter` class directly from `fastapi`:

```python
from fastapi import APIRouter
```

::: fastapi.APIRouter
    options:
        members:
            - websocket
            - include_router
            - get
            - put
            - post
            - delete
            - options
            - head
            - patch
            - trace

    options:
        members:
            - openapi_version
            - webhooks
            - state
            - dependency_overrides
            - openapi
            - websocket
            - include_router
            - get
            - put
            - post
            - delete
            - options
            - head
            - patch
            - trace
            - on_event
            - middleware

    assert response.json() == {"foo": "baz"}


def test_nested_router():
    app = FastAPI()

    router = APIRouter(prefix="/nested")

    @router.get("/test")
    async def test(var: Annotated[str, Query()] = "bar"):
        return {"foo": var}

    app.include_router(router)

    client = TestClient(app)

    response = client.get("/nested/test")