Sie verfügt über eine *Pfadoperation*, die einen `Invoice`-Body empfängt, und einen Query-Parameter `callback_url`, der die URL für den Callback enthält.

Dieser Teil ist ziemlich normal, der größte Teil des Codes ist Ihnen wahrscheinlich bereits bekannt:

{* ../../docs_src/openapi_callbacks/tutorial001.py hl[9:13,36:53] *}

/// tip | Tipp

                    logger.warn("Failed to store search parameters in cookie.", e);
                }
            }
        });
    }

    /**
     * Serializes request parameters to a compressed and encoded string.
     *
     * @param parameters Array of request parameters to serialize
     * @return Base64-encoded, GZIP-compressed JSON string of parameters
     * @throws SearchQueryException if serialization fails

{* ../../docs_src/dependencies/tutorial005_an_py310.py hl[13] *}

Let's focus on the parameters declared:

* Even though this function is a dependency ("dependable") itself, it also declares another dependency (it "depends" on something else).
    * It depends on the `query_extractor`, and assigns the value returned by it to the parameter `q`.
* It also declares an optional `last_query` cookie, as a `str`.

        buffer[37] = 0x00;
        buffer[38] = 0x00;

        // Parameter count (2 bytes)
        buffer[39] = 0x00;
        buffer[40] = 0x00;

        // Parameter offset (2 bytes)
        buffer[41] = 0x00;
        buffer[42] = 0x00;

        // Parameter displacement (2 bytes)
        buffer[43] = 0x00;
        buffer[44] = 0x00;

        // Data count (2 bytes)

Aber dieser Leitfaden zeigt Ihnen mehr oder weniger, wie die beiden normalerweise verwendet werden.

///

### Pydantics `exclude_unset`-Parameter verwenden

Wenn Sie Teil-Aktualisierungen entgegennehmen, ist der `exclude_unset`-Parameter in der `.model_dump()`-Methode von Pydantic-Modellen sehr nützlich.

Wie in `item.model_dump(exclude_unset=True)`.

/// info

   * parameters.
   */
  public MediaType withoutParameters() {
    return parameters.isEmpty() ? this : create(type, subtype);
  }

  /**
   * Replaces all parameters with the given parameters.
   *
   * @throws IllegalArgumentException if any parameter or value is invalid
   */

import java.util.Map;

/**
 * Interface for script engines that can evaluate templates with parameters.
 * This interface provides a contract for different script engine implementations
 * to process template strings with parameter substitution.
 */
public interface ScriptEngine {

    /**
     * Evaluates a template string with the provided parameter map.
     * The template is processed using the script engine's templating mechanism,

/// tip

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

Using these `dependencies` in the *path operation decorator* you can make sure they are executed while avoiding editor/tooling errors.

It might also help avoid confusion for new developers that see an unused parameter in your code and could think it's unnecessary.

///

/// info

In that case, **FastAPI** also provides you with the tools to build it.

///

When we create an instance of the `OAuth2PasswordBearer` class we pass in the `tokenUrl` parameter. This parameter contains the URL that the client (the frontend running in the user's browser) will use to send the `username` and `password` in order to get a token.

{* ../../docs_src/security/tutorial001_an_py39.py hl[8] *}

* Importieren Sie `HTMLResponse`.
* Übergeben Sie `HTMLResponse` als den Parameter `response_class` Ihres *Pfadoperation-Dekorators*.

{* ../../docs_src/custom_response/tutorial002.py hl[2,7] *}

/// info

Der Parameter `response_class` wird auch verwendet, um den „Medientyp“ der Response zu definieren.