### No Return Type { #no-return-type }

You can also omit the return type. FastAPI will use the [`jsonable_encoder`](./encoder.md) to convert the data and send it.

{* ../../docs_src/server_sent_events/tutorial001_py310.py ln[34:37] hl[35] *}

## `ServerSentEvent` { #serversentevent }

If you need to set SSE fields like `event`, `id`, `retry`, or `comment`, you can yield `ServerSentEvent` objects instead of plain data.

But normally you won't have to worry about it, it's done automatically, continue reading. 🤓

///

## Use Cases { #use-cases }

You could use this to stream data from an **AI LLM** service, from **logs** or **telemetry**, or from other types of data that can be structured in **JSON** items.

/// tip

It also includes what has changed, how validations are now more correct and strict, possible caveats, etc.

You can read it to understand better what has changed.

## Tests { #tests }

Make sure you have [tests](../tutorial/testing.md) for your app and you run them on continuous integration (CI).

This way, you can do the upgrade and make sure everything is still working as expected.

## `bump-pydantic` { #bump-pydantic }

 *
 * <h2>Repository Configuration</h2>
 *
 * <p>Repositories can be configured at various levels:</p><ol>
 * <li>POM: Repositories can be specified in the {@code pom.xml} file under the {@code <repositories>} and {@code <pluginRepositories>} sections.</li>
 * <li>Settings: the {@code settings.xml} can be used to provide additional repositories in the three level of settings (user, project, installation).</li>
 * </ol>

But this way we can focus on how the **Dependency Injection** system works.

### Create a dependency, or "dependable" { #create-a-dependency-or-dependable }

Let's first focus on the dependency.

It is just a function that can take all the same parameters that a *path operation function* can take:

{* ../../docs_src/dependencies/tutorial001_an_py310.py hl[8:9] *}

# Extra Data Types { #extra-data-types }

Up to now, you have been using common data types, like:

* `int`
* `float`
* `str`
* `bool`

But you can also use more complex data types.

And you will still have the same features as seen up to now:

* Great editor support.
* Data conversion from incoming requests.
* Data conversion for response data.
* Data validation.
* Automatic annotation and documentation.

folder using the session. The server side applications need not create a presigned URL and serve to the client for each file. Since, the client would have the session it can do it by itself.

The temporary security credentials returned by this API consists of an access key, a secret key, and a security token. Applications can use these temporary security credentials to sign calls to MinIO API operations. The policy applied to these temporary credentials is inherited from the MinIO user credentials....

It is possible to receive duplicate headers. That means, the same header with multiple values.

You can define those cases using a list in the type declaration.

You will receive all the values from the duplicate header as a Python `list`.

For example, to declare a header of `X-Token` that can appear more than once, you can write:

{* ../../docs_src/header_params/tutorial003_an_py310.py hl[9] *}

That defines the metadata about the main response of a *path operation*.

You can also declare additional responses with their models, status codes, etc.

There's a whole chapter here in the documentation about it, you can read it at [Additional Responses in OpenAPI](additional-responses.md).

## OpenAPI Extra { #openapi-extra }

    /**
     * Determines the address of a host given it's host name. The name can be a NetBIOS name like
     * "freto" or an IP address like "192.168.1.15". It cannot be a DNS name;
     * the analygous {@link jcifs.netbios.UniAddress} or {@link java.net.InetAddress}
     * <code>getByName</code> methods can be used for that.
     *
     * @param host
     *            hostname to resolve