override fun cancel() {
    call!!.cancel()
  }

  fun connect(client: OkHttpClient) {
    if (originalRequest.header("Sec-WebSocket-Extensions") != null) {
      failWebSocket(ProtocolException("Request header not permitted: 'Sec-WebSocket-Extensions'"))
      return
    }

    val webSocketClient =
      client.newBuilder()
        .eventListener(EventListener.NONE)
        .protocols(ONLY_HTTP1)

And there are dozens of alternatives, all based on OpenAPI. You could easily add any of those alternatives to your application built with **FastAPI**.

You could also use it to generate code automatically, for clients that communicate with your API. For example, frontend, mobile or IoT applications.

## Recap, step by step

### Step 1: import `FastAPI`

```Python hl_lines="1"
{!../../../docs_src/first_steps/tutorial001.py!}

	// TODO: It seems like we may have to be prepared to rewrite and sort trailing headers:
	// https://docs.aws.amazon.com/IAM/latest/UserGuide/create-signed-request.html

	// Any value must end with a newline.
	// Not all clients send that.
	trailerRaw := valueBuffer.Bytes()
	if len(trailerRaw) > 0 && trailerRaw[len(trailerRaw)-1] != '\n' {
		valueBuffer.Write([]byte{'\n'})
	}
	sig = sig[len("x-amz-trailer-signature:"):]

Dies wird **FastAPI** wissen lassen, dass dieser Parameter erforderlich ist.

### Erforderlich, kann `None` sein

Sie können deklarieren, dass ein Parameter `None` akzeptiert, aber dennoch erforderlich ist. Das zwingt Clients, den Wert zu senden, selbst wenn er `None` ist.

Um das zu machen, deklarieren Sie, dass `None` ein gültiger Typ ist, aber verwenden Sie dennoch `...` als Default:

=== "Python 3.10+"

    ```Python hl_lines="9"

import "k8s.io/apimachinery/pkg/util/intstr/generated.proto";

// Package-wide variables from generator "generated".
option go_package = "k8s.io/api/apps/v1";

// ControllerRevision implements an immutable snapshot of state data. Clients
// are responsible for serializing and deserializing the objects that contain
// their internal state.
// Once a ControllerRevision has been successfully created, it can not be updated.

                        iterator.remove();
                        notified = true;

                    }
                    if ( notified ) {
                        log.debug("Notified clients");
                    }
                    else {
                        log.debug("Exception without a request pending", ex);
                    }
                    return;
                }

}

// PopHealStatusJSON - Called by heal-status API. It fetches the heal
// status results from global state and returns its JSON
// representation. The clientToken helps ensure there aren't
// conflicting clients fetching status.
func (ahs *allHealState) PopHealStatusJSON(hpath string,
	clientToken string) ([]byte, APIErrorCode,
) {
	// fetch heal state for given path
	h, exists := ahs.getHealSequence(hpath)
	if !exists {

	if errors.As(err, &r) {
		return &r
	}
	return nil
}

type (
	// SingleHandlerFn is handlers for one to one requests.
	// A non-nil error value will be returned as RemoteErr(msg) to client.
	// No client information or cancellation (deadline) is available.
	// Include this in payload if needed.
	// Payload should be recycled with PutByteBuffer if not needed after the call.

	writeSuccessResponseXML(w, encodedSuccessResponse)
}

// AssumeRoleWithCertificate implements user authentication with client certificates.
// It verifies the client-provided X.509 certificate, maps the certificate to an S3 policy
// and returns temp. S3 credentials to the client.
//
// API endpoint: https://minio:9000?Action=AssumeRoleWithCertificate&Version=2011-06-15

	// S3 also supports the older SelectObjectContentRequest tag,
	// though it is no longer found in documentation. This is
	// checked and renamed below to allow older clients to also
	// work.
	if start.Name.Local == legacyXMLName {
		start.Name = xml.Name{Space: "", Local: "SelectRequest"}
	}

	// Make subtype to avoid recursive UnmarshalXML().
	type subS3Select S3Select