// value of true indicates that the list was truncated. The list can be truncated
	// if the number of objects exceeds the limit allowed or specified
	// by max keys.
	IsTruncated bool

	// When response is truncated (the IsTruncated element value in the response is true),
	// you can use the key name in this field as marker in the subsequent
	// request to get next set of objects.
	//

You can use the Select API to query objects with following features:

- Objects must be in CSV, JSON, or Parquet(*) format.
- UTF-8 is the only encoding type the Select API supports.

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){.internal-link target=_blank}.

## OpenAPI Extra { #openapi-extra }

We could do better.

We can declare a `UserBase` model that serves as a base for our other models. And then we can make subclasses of that model that inherit its attributes (type declarations, validation, etc).

All the data conversion, validation, documentation, etc. will still work as normally.

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] *}

* Data validation
* Automatic documentation

## Defaults { #defaults }

As query parameters are not a fixed part of a path, they can be optional and can have default values.

In the example above they have default values of `skip=0` and `limit=10`.

So, going to the URL:

```
http://127.0.0.1:8000/items/
```

would be the same as going to:

    // Running at time 50, the pool returns that nothing can be evicted until time 150.
    assertThat(pool.closeConnections(50L)).isEqualTo(100L)
    assertThat(pool.connectionCount()).isEqualTo(1)
    assertThat(c1.socket().isClosed).isFalse()

    // Running at time 60, the pool returns that nothing can be evicted until time 150.
    assertThat(pool.closeConnections(60L)).isEqualTo(90L)

If you would like to contribute code to OkHttp you can do so through GitHub by
forking the repository and sending a pull request.

When submitting code, please make every effort to follow existing conventions
and style in order to keep the code as readable as possible. Please also make
sure your code compiles by running `./gradlew check`. Checkstyle failures
during compilation indicate errors in your style and can be viewed in the
`checkstyle-result.xml` file.

You can use the same type declarations with `str`, `float`, `bool` and many other complex data types.

Several of these are explored in the next chapters of the tutorial.

## Order matters { #order-matters }

When creating *path operations*, you can find situations where you have a fixed path.

## Check the Docs { #check-the-docs }

You can see the required headers in the docs UI at `/docs`:

<div class="screenshot">
<img src="/img/tutorial/header-param-models/image01.png">
</div>

## Forbid Extra Headers { #forbid-extra-headers }

In some special use cases (probably not very common), you might want to **restrict** the headers that you want to receive.