You can also declare the `Response` parameter in dependencies, and set headers (and cookies) in them.

## Return a `Response` directly { #return-a-response-directly }

You can also add headers when you return a `Response` directly.

Create a response as described in [Return a Response Directly](response-directly.md) and pass the headers as an additional parameter:

{* ../../docs_src/response_headers/tutorial001_py310.py hl[10:12] *}

    }

    /**
     * A transformation to replace the key in a do section.
     *
     * @param oldKeyName the key name directly under do to replace.
     * @param newKeyName the new key name directly under do.
     * @param testName   the testName to apply replacement
     * @see ReplaceKeyInDo
     */

```Python
contents = myfile.file.read()
```

/// note | `async` Technical Details

When you use the `async` methods, **FastAPI** runs the file methods in a threadpool and awaits for them.

///

/// note | Starlette Technical Details

name: Privileged
description: You are @tiangolo or he asked you directly to create an issue here. If not, check the other options. 👇
body:
  - type: markdown
    attributes:
      value: |
        Thanks for your interest in FastAPI! 🚀

        If you are not @tiangolo or he didn't ask you directly to create an issue here, please start the conversation in a [Question in GitHub Discussions](https://github.com/fastapi/fastapi/discussions/categories/questions) instead.

You can use the `TestClient` class to test FastAPI applications without creating an actual HTTP and socket connection, just communicating directly with the FastAPI code.

Read more about it in the [FastAPI docs for Testing](https://fastapi.tiangolo.com/tutorial/testing/).

You can import it directly from `fastapi.testclient`:

```python
from fastapi.testclient import TestClient
```

Remember that dependencies can have sub-dependencies?

`get_current_user` will have a dependency with the same `oauth2_scheme` we created before.

The same as we were doing before in the *path operation* directly, our new dependency `get_current_user` will receive a `token` as a `str` from the sub-dependency `oauth2_scheme`:

{* ../../docs_src/security/tutorial002_an_py310.py hl[25] *}

## Get the user { #get-the-user }

Additional classes for handling WebSockets.

Provided directly by Starlette, but you can import it from `fastapi`:

```python
from fastapi.websockets import WebSocketDisconnect, WebSocketState
```

::: fastapi.websockets.WebSocketDisconnect

When a client disconnects, a `WebSocketDisconnect` exception is raised, you can catch it.

You can import it directly form `fastapi`:

```python

try:
    import orjson
except ImportError:  # pragma: nocover
    orjson = None  # type: ignore


@deprecated(
    "UJSONResponse is deprecated, FastAPI now serializes data directly to JSON "
    "bytes via Pydantic when a return type or response model is set, which is "
    "faster and doesn't need a custom response class. Read more in the FastAPI "

## `Depends()`

Dependencies are handled mainly with the special function `Depends()` that takes a callable.

Here is the reference for it and its parameters.

You can import it directly from `fastapi`:

```python
from fastapi import Depends
```

::: fastapi.Depends

## `Security()`

///

## Run your code with your debugger { #run-your-code-with-your-debugger }

Because you are running the Uvicorn server directly from your code, you can call your Python program (your FastAPI application) directly from the debugger.

---

For example, in Visual Studio Code, you can:

* Go to the "Debug" panel.
* "Add configuration...".
* Select "Python"