from fastapi import FastAPI, Response

app = FastAPI()


@app.get("/headers-and-object/")
def get_headers(response: Response):
    response.headers["X-Cat-Dog"] = "alone in the world"

from fastapi import FastAPI
from fastapi.responses import JSONResponse

app = FastAPI()


@app.get("/headers/")
def get_headers():
    content = {"message": "Hello World"}
    headers = {"X-Cat-Dog": "alone in the world", "Content-Language": "en-US"}

def test_path_operation():
    response = client.get("/headers-and-object/")
    assert response.status_code == 200, response.text
    assert response.json() == {"message": "Hello World"}

def test_path_operation():
    response = client.get("/headers/")
    assert response.status_code == 200, response.text
    assert response.json() == {"message": "Hello World"}
    assert response.headers["X-Cat-Dog"] == "alone in the world"

It's still possible to use `BackgroundTask` alone in FastAPI, but you have to create the object in your code and return a Starlette `Response` including it.

```Dockerfile
CMD ["uvicorn", "app.main:app", "--proxy-headers", "--host", "0.0.0.0", "--port", "80"]
```

#### Docker Cache

There's an important trick in this `Dockerfile`, we first copy the **file with the dependencies alone**, not the rest of the code. Let me tell you why is that.

```Dockerfile
COPY ./requirements.txt /code/requirements.txt
```

        app = FastAPI()
        router = APIRouter()

        @router.head("/items/", status_code=204)
        def get_items_headers(response: Response):
            response.headers["X-Cat-Dog"] = "Alone in the world"

        app.include_router(router)
        ```
        """
        return self.api_route(
            path=path,
            response_model=response_model,

        app = FastAPI()

        @app.head("/items/", status_code=204)
        def get_items_headers(response: Response):
            response.headers["X-Cat-Dog"] = "Alone in the world"
        ```
        """
        return self.router.head(
            path,
            response_model=response_model,
            status_code=status_code,
            tags=tags,

    ```

!!! note
    Keep in mind that in this case, FastAPI won't check the contents of the list.

    For example, `List[int]` would check (and document) that the contents of the list are integers. But `list` alone wouldn't.

## Declare more metadata

You can add more information about the parameter.

That information will be included in the generated OpenAPI and used by the documentation user interfaces and external tools.