/// tip

Pydantic có một hành vi đặc biệt khi bạn sử dụng `Optional` hoặc `Union[Something, None]` mà không có giá trị mặc dịnh, bạn có thể đọc nhiều hơn về nó trong tài liệu của Pydantic về <a href="https://docs.pydantic.dev/latest/concepts/models/#required-optional-fields" class="external-link" target="_blank">Required Optional fields</a>.

///

## Type Hints với Metadata Annotations

	// Content-Md5 is required should be set
	// http://docs.aws.amazon.com/AmazonS3/latest/API/multiobjectdeleteapi.html
	if !validateLengthAndChecksum(r) {
		writeErrorResponse(ctx, w, errorCodes.ToAPIErr(ErrMissingContentMD5), r.URL)
		return
	}

	// Content-Length is required and should be non-zero
	// http://docs.aws.amazon.com/AmazonS3/latest/API/multiobjectdeleteapi.html
	if r.ContentLength <= 0 {

이를 위해 표준 Python 타입 힌트인 <a href="https://docs.python.org/3/library/typing.html#typing.Union" class="external-link" target="_blank">`typing.Union`</a>을 사용할 수 있습니다:

/// note | 참고

<a href="https://docs.pydantic.dev/latest/concepts/types/#unions" class="external-link" target="_blank">`Union`</a>을 정의할때는 더 구체적인 타입을 먼저 포함하고, 덜 구체적인 타입을 그 뒤에 나열해야합니다. 아래 예제에서는 `Union[PlaneItem, CarItem]` 를 보면, 더 구체적인 `PlaneItem`이 `CarItem`보다 앞에 위치합니다.

///

/// warning

These are technical details that you might skip if it's not important for you now.

///

`RequestValidationError` is a sub-class of Pydantic's <a href="https://docs.pydantic.dev/latest/concepts/models/#error-handling" class="external-link" target="_blank">`ValidationError`</a>.

* `write(daten)`: Schreibt `daten` (`str` oder `bytes`) in die Datei.
* `read(anzahl)`: Liest `anzahl` (`int`) bytes/Zeichen aus der Datei.
* `seek(versatz)`: Geht zur Position `versatz` (`int`) in der Datei.
    * Z. B. würde `await myfile.seek(0)` zum Anfang der Datei gehen.

      <version>1.0.0+</version>
      <description>Versioning information for "groupId/artifactId" or "groupId/artifactId/version" SNAPSHOT</description>
      <fields>
        <field>
          <name>latest</name>
          <version>1.0.0+</version>
          <type>String</type>

	if field, ok := schema.FieldsByDBName[name]; ok {
		return field
	}
	if field, ok := schema.FieldsByName[name]; ok {
		return field
	}
	return nil
}

// LookUpFieldByBindName looks for the closest field in the embedded struct.
//
//	type Struct struct {
//		Embedded struct {
//			ID string // is selected by LookUpFieldByBindName([]string{"Embedded", "ID"}, "ID")
//		}

/// info

Wenn Sie bereits das ganze Tutorial durchgearbeitet haben und mehr über Typen erfahren wollen, dann ist eine gute Ressource <a href="https://mypy.readthedocs.io/en/latest/cheat_sheet_py3.html" class="external-link" target="_blank">der „Cheat Sheet“ von `mypy`</a>.

/// tip | Dica

O SQLModel terá utilitários de migração envolvendo o Alembic, mas por enquanto, você pode usar o <a href="https://alembic.sqlalchemy.org/en/latest/" class="external-link" target="_blank">Alembic</a> diretamente.

///

### Criar um Hero

region   (string)    name of the location of the server e.g. "us-west-1"
comment  (sentence)  optionally add a comment to this setting
```

or environment variables

```
KEY:
site  label the server and its location

ARGS:
MINIO_SITE_NAME     (string)    name for the site e.g. "cal-rack0"
MINIO_SITE_REGION   (string)    name of the location of the server e.g. "us-west-1"