You can also combine `dataclasses` with other type annotations to make nested data structures.

In some cases, you might still have to use Pydantic's version of `dataclasses`. For example, if you have errors with the automatically generated API documentation.

In that case, you can simply swap the standard `dataclasses` with `pydantic.dataclasses`, which is a drop-in replacement:

app = SomeASGIApp()

new_app = UnicornMiddleware(app, some_config="rainbow")
```

But FastAPI (actually Starlette) provides a simpler way to do it that makes sure that the internal middlewares handle server errors and custom exception handlers work properly.

For that, you use `app.add_middleware()` (as in the example for CORS).

```Python
from fastapi import FastAPI
from unicorn import UnicornMiddleware

app = FastAPI()

package lifecycle

import (
	"encoding/xml"
	"fmt"
	"testing"

	"github.com/dustin/go-humanize"
)

// TestUnsupportedFilters checks if parsing Filter xml with
// unsupported elements returns appropriate errors
func TestUnsupportedFilters(t *testing.T) {
	testCases := []struct {
		inputXML    string
		expectedErr error
	}{
		{ // Filter with And tags
			inputXML: ` <Filter>
						<And>

  echo '==TFCI==: The $TFCI variable is not set. This is fine as long as you'
  echo 'already sourced a TFCI env file with "set -a; source <path>; set +a".'
  echo 'If you have not, you will see a lot of undefined variable errors.'
else
  FROM_ENV=$(mktemp)
  # "export -p" prints a list of environment values in a safe-to-source format,
  # e.g. `declare -x TFCI_BAZEL_COMMON_ARGS="list of args"` for bash.
  export -p | grep TFCI > "$FROM_ENV"

하지만 필요한 경우 사용할 수 있습니다. 🤓

///

{* ../../docs_src/dependencies/tutorial008b_an_py39.py hl[18:22,31] *}

예외를 처리하고(또는 추가로 다른 `HTTPException`을 발생시키기 위해) 사용할 수 있는 또 다른 방법은 [사용자 정의 예외 처리기](../handling-errors.md#install-custom-exception-handlers){.internal-link target=_blank}를 생성하는 것 입니다.

## `yield`와 `except`를 사용하는 의존성

	. "gorm.io/gorm/utils/tests"
)

func TestMany2ManyAssociation(t *testing.T) {
	user := *GetUser("many2many", Config{Languages: 2})

	if err := DB.Create(&user).Error; err != nil {
		t.Fatalf("errors happened when create: %v", err)
	}

	CheckUser(t, user, user)

	// Find
	var user2 User
	DB.Find(&user2, "id = ?", user.ID)
	DB.Model(&user2).Association("Languages").Find(&user2.Languages)

这是一种相对高级的技巧，在大多数情况下你并不需要使用它，因为你可以在其他代码中抛出异常（包括 `HTTPException` ），例如在 *路由函数* 中。

但是如果你需要，你也可以在依赖项中做到这一点。🤓

///

{* ../../docs_src/dependencies/tutorial008b_an_py39.py hl[18:22,31] *}

你还可以创建一个 [自定义异常处理器](../handling-errors.md#install-custom-exception-handlers){.internal-link target=_blank} 用于捕获异常（同时也可以抛出另一个 `HTTPException`）。

## 包含 `yield` 和 `except` 的依赖项

/// note

FastAPI will know that the value of `q` is not required because of the default value `= None`.

Having `str | None` will allow your editor to give you better support and detect errors.

///

## Additional validation { #additional-validation }

We are going to enforce that even though `q` is optional, whenever it is provided, **its length doesn't exceed 50 characters**.

/// tip | Dica

Para resolver esse mesmo problema, é provavelmente muito mais fácil usar o `body` em um manipulador personalizado para `RequestValidationError` ([Tratando Erros](../tutorial/handling-errors.md#use-the-requestvalidationerror-body){.internal-link target=_blank}).

Mas esse exemplo ainda é valido e mostra como interagir com os componentes internos.

///

import java.util.Locale;
import java.util.Properties;

import org.apache.maven.jline.MessageUtils;
import org.apache.maven.utils.Os;
import org.slf4j.Logger;

/**
 * Utility class used to report errors, statistics, application version info, etc.
 *
 */
@Deprecated
public final class CLIReportingUtils {
    // CHECKSTYLE_OFF: MagicNumber
    public static final long MB = 1024 * 1024;