*       typically because the type forbids nullable type arguments: For example, {@code
 *       ImmutableList.get} returns {@code E}, but that value is never {@code null}. (Accordingly,
 *       {@code ImmutableList} is declared to forbid {@code ImmutableList<@Nullable String>}.)
 *   <li>methods whose return type is a type variable but which can return {@code null} regardless
 *       of the type argument supplied by the user of the class: For example, {@code

 *       typically because the type forbids nullable type arguments: For example, {@code
 *       ImmutableList.get} returns {@code E}, but that value is never {@code null}. (Accordingly,
 *       {@code ImmutableList} is declared to forbid {@code ImmutableList<@Nullable String>}.)
 *   <li>methods whose return type is a type variable but which can return {@code null} regardless
 *       of the type argument supplied by the user of the class: For example, {@code

 *       typically because the type forbids nullable type arguments: For example, {@code
 *       ImmutableList.get} returns {@code E}, but that value is never {@code null}. (Accordingly,
 *       {@code ImmutableList} is declared to forbid {@code ImmutableList<@Nullable String>}.)
 *   <li>methods whose return type is a type variable but which can return {@code null} regardless
 *       of the type argument supplied by the user of the class: For example, {@code

 *       typically because the type forbids nullable type arguments: For example, {@code
 *       ImmutableList.get} returns {@code E}, but that value is never {@code null}. (Accordingly,
 *       {@code ImmutableList} is declared to forbid {@code ImmutableList<@Nullable String>}.)
 *   <li>methods whose return type is a type variable but which can return {@code null} regardless
 *       of the type argument supplied by the user of the class: For example, {@code

 *       typically because the type forbids nullable type arguments: For example, {@code
 *       ImmutableList.get} returns {@code E}, but that value is never {@code null}. (Accordingly,
 *       {@code ImmutableList} is declared to forbid {@code ImmutableList<@Nullable String>}.)
 *   <li>methods whose return type is a type variable but which can return {@code null} regardless
 *       of the type argument supplied by the user of the class: For example, {@code

	// Broadcast without memory operand.
	VADDPD.BCST X3, X2, K1, X1       // ERROR "illegal broadcast without memory argument"
	VADDPD.BCST X3, X2, K1, X1       // ERROR "illegal broadcast without memory argument"
	VADDPD.BCST X3, X2, K1, X1       // ERROR "illegal broadcast without memory argument"
	// CLWB instructions:
	CLWB BX                          // ERROR "invalid instruction"
	// CLDEMOTE instructions:

from unicorn import UnicornMiddleware

app = FastAPI()

app.add_middleware(UnicornMiddleware, some_config="rainbow")
```

`app.add_middleware()` receives a middleware class as the first argument and any additional arguments to be passed to the middleware.

## Integrated middlewares { #integrated-middlewares }

**FastAPI** includes several middlewares for common use cases, we'll see next how to use them.

### `Union` in Python 3.10 { #union-in-python-3-10 }

In this example we pass `Union[PlaneItem, CarItem]` as the value of the argument `response_model`.

Because we are passing it as a **value to an argument** instead of putting it in a **type annotation**, we have to use `Union` even in Python 3.10.

If it was in a type annotation we could have used the vertical bar, as:

```Python

          fileSystem.source(this@asRequestBody).use { source -> sink.writeAll(source) }
        }
      }

    @JvmStatic
    @Deprecated(
      message = "Moved to extension function. Put the 'content' argument first to fix Java",
      replaceWith =
        ReplaceWith(
          expression = "content.toRequestBody(contentType)",
          imports = ["okhttp3.RequestBody.Companion.toRequestBody"],
        ),

Auf diese Weise erhalten wir ein Pydantic-Modell aus den Daten eines anderen Pydantic-Modells.

#### Ein `dict` entpacken und zusätzliche Schlüsselwort-Argumente { #unpacking-a-dict-and-extra-keywords }

Und dann fügen wir das zusätzliche Schlüsselwort-Argument `hashed_password=hashed_password` hinzu, wie in:

```Python
UserInDB(**user_in.model_dump(), hashed_password=hashed_password)
```

... was so ist wie: