return value + 100;
        }
    }

    /**
     * Display attributes, also know as
     * <a href="https://en.wikipedia.org/wiki/ANSI_escape_code#SGR_(Select_Graphic_Rendition)_parameters">SGR
     * (Select Graphic Rendition) parameters</a>.
     */
    public enum Attribute {
        RESET(0, "RESET"),
        INTENSITY_BOLD(1, "INTENSITY_BOLD"),
        INTENSITY_FAINT(2, "INTENSITY_FAINT"),
        ITALIC(3, "ITALIC_ON"),

<p>
A function type denotes the set of all functions with the same parameter
and result types. The value of an uninitialized variable of function type
is <code>nil</code>.
</p>

<pre class="ebnf">
FunctionType   = "func" Signature .
Signature      = Parameters [ Result ] .
Result         = Parameters | Type .
Parameters     = "(" [ ParameterList [ "," ] ] ")" .

    }

    /**
     * Creates a shallow copy of this parameter.
     */
    @Override
    public Parameter clone() {
        try {
            return (Parameter) super.clone();
        } catch (CloneNotSupportedException e) {
            throw new UnsupportedOperationException(e);
        }
    }

    public org.apache.maven.api.plugin.descriptor.Parameter getParameterV4() {

func (l *List[T]) Len() int  { … }
</pre>

<h3 id="Type_parameter_declarations">Type parameter declarations</h3>

<p>
A type parameter list declares the <i>type parameters</i> of a generic function or type declaration.
The type parameter list looks like an ordinary <a href="#Function_types">function parameter list</a>
except that the type parameter names must all be present and the list is enclosed
in square brackets rather than parentheses

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

  /**

der wichtigste Teil ist, um einen Parameter optional zu machen, da dieses `None` der Defaultwert ist, und das ist es, was diesen Parameter **nicht erforderlich** macht.

Der Teil mit `Union[str, None]` erlaubt es Ihrem Editor, Sie besser zu unterstützen, aber er sagt FastAPI nicht, dass dieser Parameter optional ist.

///

Jetzt können wir `Query` weitere Parameter übergeben. Fangen wir mit dem `max_length` Parameter an, der auf Strings angewendet wird:

# Path Parameters and Numeric Validations

In the same way that you can declare more validations and metadata for query parameters with `Query`, you can declare the same type of validations and metadata for path parameters with `Path`.

## Import Path

First, import `Path` from `fastapi`, and import `Annotated`:

//// tab | Python 3.10+

```Python hl_lines="1  3"
{!> ../../docs_src/path_params_numeric_validations/tutorial001_an_py310.py!}
```

# Query Parameter Models

If you have a group of **query parameters** that are related, 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`. 🤓

///

## Query Parameters with a Pydantic Model

Wenn im Request ein Query-Parameter enthalten war, wird dieser in einem Hintergrundtask in das Log geschrieben.

Und dann schreibt ein weiterer Hintergrundtask, der in der *Pfadoperation-Funktion* erstellt wird, eine Nachricht unter Verwendung des Pfad-Parameters `email`.

## Technische Details

# Body - Multiple Parameters

Now that we have seen how to use `Path` and `Query`, let's see more advanced uses of request body declarations.

## Mix `Path`, `Query` and body parameters

First, of course, you can mix `Path`, `Query` and request body parameter declarations freely and **FastAPI** will know what to do.

And you can also declare body parameters as optional, by setting the default to `None`:

//// tab | Python 3.10+