# Header Parameter Models { #header-parameter-models }

If you have a group of related **header parameters**, you can create a **Pydantic model** to declare them.

This would allow you to **re-use the model** in **multiple places** and also to declare validations and metadata for all the parameters at once. 😎

/// note

This is supported since FastAPI version `0.115.0`. 🤓

///

    }

    private Stream<String> getParameterNames(Parameter parameter) {
        if (parameter.getAlias() != null) {
            return Stream.of(parameter.getName(), parameter.getAlias());
        } else {
            return Stream.of(parameter.getName());
        }
    }

    private Set<String> getUnknownParameters(MojoExecution mojoExecution, Set<String> parameters) {

# Response Cookies { #response-cookies }

## Use a `Response` parameter { #use-a-response-parameter }

You can declare a parameter of type `Response` in your *path operation function*.

And then you can set cookies in that *temporal* response object.

{* ../../docs_src/response_cookies/tutorial002_py39.py hl[1, 8:9] *}

And then you can return any object you need, as you normally would (a `dict`, a database model, etc).

 * types, and also for interfaces and public classes that have public parameter-less constructors.
 * When the non-null default value for a particular parameter type cannot be provided by {@code
 * NullPointerTester}, the caller can provide a custom non-null default value for the parameter type
 * via {@link #setDefault}.
 *
 * @author Kevin Bourrillion
 * @since 10.0
 */
@GwtIncompatible

    private final Map<String, Parameter> missingParameters;

    ValidatingConfigurationListener(Object mojo, MojoDescriptor mojoDescriptor, ConfigurationListener delegate) {
        this.mojo = mojo;
        this.delegate = delegate;
        this.missingParameters = new HashMap<>();

        if (mojoDescriptor.getParameters() != null) {
            for (Parameter param : mojoDescriptor.getParameters()) {

   * the dummy value of a constructor or method parameter is unknown.
   */
  @VisibleForTesting
  static final class ParameterNotInstantiableException extends Exception {
    public ParameterNotInstantiableException(Parameter parameter) {
      super(
          "Cannot determine value for parameter "
              + parameter
              + " of "
              + parameter.getDeclaringInvokable());
    }
  }

        </field>
      </fields>
    </class>

    <class xdoc.anchorName="parameter">
      <name>Parameter</name>
      <version>1.0.0+</version>
      <description>A parameter description.</description>
      <!-- see o.a.m.plugin.descriptor.Parameter -->
      <fields>
        <field>
          <name>name</name>
          <version>1.0.0+</version>

## List fields with type parameter { #list-fields-with-type-parameter }

But Python has a specific way to declare lists with internal types, or "type parameters":

### Declare a `list` with a type parameter { #declare-a-list-with-a-type-parameter }

To declare types that have type parameters (internal types), like `list`, `dict`, `tuple`,
pass the internal type(s) as "type parameters" using square brackets: `[` and `]`

```Python

Wenn Sie **FastAPI** ein „Callable“ als Abhängigkeit übergeben, analysiert es die Parameter dieses „Callables“ und verarbeitet sie auf die gleiche Weise wie die Parameter einer *Pfadoperation-Funktion*. Einschließlich Unterabhängigkeiten.

Das gilt auch für Callables ohne Parameter. So wie es auch für *Pfadoperation-Funktionen* ohne Parameter gilt.

/// info | Info

`Form` ist eine Klasse, die direkt von `Body` erbt.

///

/// tip | Tipp

Um Formularbodys zu deklarieren, verwenden Sie explizit `Form`, da diese Parameter sonst als Query-Parameter oder Body (JSON)-Parameter interpretiert werden würden.

///

## Über „Formularfelder“ { #about-form-fields }