* However, we can't usually write {@code throw t;} when {@code t} has a static type of {@link
   * Throwable}. But we <i>can</i> write {@code sneakyThrow(t);}.
   *
   * <p>We sometimes also use {@code sneakyThrow} for testing how our code responds to
   * sneaky checked exception.
   *
   * @return never; this method declares a return type of {@link Error} only so that callers can

        }
    ]
}
```

/// info

Notice how the `images` key now has a list of image objects.

///

## Deeply nested models { #deeply-nested-models }

You can define arbitrarily deeply nested models:

{* ../../docs_src/body_nested_models/tutorial007_py310.py hl[7,12,18,21,25] *}

/// info

Notice how `Offer` has a list of `Item`s, which in turn have an optional list of `Image`s

So, about the egg and the chicken, how do you call the first `async` function?

If you are working with **FastAPI** you don't have to worry about that, because that "first" function will be your *path operation function*, and FastAPI will know how to do the right thing.

But if you want to use `async` / `await` without FastAPI, you can do it as well.

/** Runs the web platform URL tests against Java URL models.  */
class WebPlatformUrlTest {
  class TestDataParamProvider : SimpleProvider() {
    override fun arguments() = ArrayList<Any>(loadTests())
  }

  /** Test how [HttpUrl] does against the web platform test suite.  */
  @ArgumentsSource(TestDataParamProvider::class)
  @ParameterizedTest
  fun httpUrl(testData: WebPlatformUrlTestData) {

   * code would be responsible for populating a "real" {@code T} (which might still be the value
   * {@code null}!) before returning it to callers. Depending on how the code is structured, a
   * nullness analysis might not understand that the field has been populated. To avoid that problem
   * without having to add {@code @SuppressWarnings}, the code can call this method.
   *

All these, while minimizing code repetition.

## First Steps { #first-steps }

Let's see a very simple example. It will be so simple that it is not very useful, for now.

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.

# Extending OpenAPI { #extending-openapi }

There are some cases where you might need to modify the generated OpenAPI schema.

In this section you will see how.

## The normal process { #the-normal-process }

The normal (default) process, is as follows.

A `FastAPI` application (instance) has an `.openapi()` method that is expected to return the OpenAPI schema.

 * {@code NtlmServlet}, and {@code NetworkExplorer} to negotiate password
 * hashes via NTLM SSP with MSIE. It might also be used directly by servlet
 * containers to incorporate similar functionality.
 * <p>
 * How NTLMSSP is used in conjunction with HTTP and MSIE clients is
 * described in an <A HREF="http://www.innovation.ch/java/ntlm.html">NTLM
 * Authentication Scheme for HTTP</A>.
 * <p>
 * Also, read <a

{* ../../docs_src/path_operation_configuration/tutorial006.py hl[16] *}

It will be clearly marked as deprecated in the interactive docs:

<img src="/img/tutorial/path-operation-configuration/image04.png">

Check how deprecated and non-deprecated *path operations* look like:

<img src="/img/tutorial/path-operation-configuration/image05.png">

## Recap { #recap }

 *
 * Despite its name, [java.net.URL.getProtocol] returns the [scheme][java.net.URI.getScheme] (http,
 * https, etc.) of the URL, not the protocol (http/1.1, spdy/3.1, etc.). OkHttp uses the word
 * *protocol* to identify how HTTP messages are framed.
 *
 * [ietf_alpn]: http://tools.ietf.org/html/draft-ietf-tls-applayerprotoneg
 */
enum class Protocol(
  private val protocol: String,
) {
  /**