///

## **FastAPI** utilities

FastAPI provides several tools for each of these security schemes in the `fastapi.security` module that simplify using these security mechanisms.

In the next chapters you will see how to add security to your API using those tools provided by **FastAPI**.

<img src="/img/tutorial/extending-openapi/image03.png">

## Change the Theme

The same way you could set the syntax highlighting theme with the key `"syntaxHighlight.theme"` (notice that it has a dot in the middle):

{* ../../docs_src/configure_swagger_ui/tutorial002.py hl[3] *}

That configuration would change the syntax highlighting color theme:

<img src="/img/tutorial/extending-openapi/image04.png">

  The `NewDelayedInformer` abstracts that entirely, offering the same API as normal `kclient.Client`.
* Simple object filtering. Beyond just static filters on objects, `kclient` supports _dynamic filters_ that can change at runtime.
  When a filter changes and includes/removes new objects, those are automatically handled.

{% endfor %}

</div>
{% endif %}

There are many other contributors (more than a hundred), you can see them all in the <a href="https://github.com/fastapi/fastapi/graphs/contributors" class="external-link" target="_blank">FastAPI GitHub Contributors page</a>. 👷

## Top Translation Reviewers

These users are the **Top Translation Reviewers**. 🕵️

* **`300`** and above are for "Redirection".  Responses with these status codes may or may not have a body, except for `304`, "Not Modified", which must not have one.
* **`400`** and above are for "Client error" responses. These are the second type you would probably use the most.
    * An example is `404`, for a "Not Found" response.

These are the exceptions that you can raise to show errors to the client.

When you raise an exception, as would happen with normal Python, the rest of the execution is aborted. This way you can raise these exceptions from anywhere in the code to abort a request and show the error to the client.

You can use:

* `HTTPException`
* `WebSocketException`

These exceptions can be imported directly from `fastapi`:

# https://github.com/Danimoth/gitattributes

# These are explicitly windows files and should use crlf
*.bat           text eol=crlf

# These files are text and should be normalized (Convert crlf => lf)
*.bash          text eol=lf
*.css           text diff=css
*.htm           text diff=html
*.html          text diff=html
*.java          text diff=java
*.sh            text eol=lf


# These files are binary and should be left untouched

        # [Include]
        # String columns may not be needed
        # to be set these condition-keys basically.
        #; GreaterThan = map:{}
        #; LessThan = map:{}
        #; GreaterEqual = map:{}
        #; LessEqual = map:{}

        # [Exclude]
        # Common columns of String type may not be needed
        # to be set these condition-keys basically.
        #; !NotEqual = map:{ $$ALL$$ = list:{ $$CommonColumn$$ } }

This is similar to the 200 HTTP status codes (from 200 to 299). Those "200" status codes mean that somehow there was a "success" in the request.

The status codes in the 400 range mean that there was an error from the client.

Remember all those **"404 Not Found"** errors (and jokes)?

## Use `HTTPException`

```Python hl_lines="17"
{!> ../../docs_src/dependencies/tutorial006.py!}
```

////

These dependencies will be executed/solved the same way as normal dependencies. But their value (if they return any) won't be passed to your *path operation function*.

/// tip

Some editors check for unused function parameters, and show them as errors.