Despite this expectation in SotW, due to a quirk in the protocol we can actually enable one of our most important optimizations. XDS types form a tree, with CDS and LDS the root of the tree for Envoy. For root types, we *must* always generate the full set of resources - missing resources are treated as deletions.

/// 정보

`OAuth2PasswordRequestForm`은 `OAuth2PasswordBearer`와 같이 **FastAPI**에 대한 특수 클래스가 아닙니다.

`OAuth2PasswordBearer`는 **FastAPI**가 보안 체계임을 알도록 합니다. 그래서 OpenAPI에 그렇게 추가됩니다.

그러나 `OAuth2PasswordRequestForm`은 직접 작성하거나 `Form` 매개변수를 직접 선언할 수 있는 클래스 의존성일 뿐입니다.

그러나 일반적인 사용 사례이므로 더 쉽게 하기 위해 **FastAPI**에서 직접 제공합니다.

///

### 폼 데이터 사용하기

/// 팁

	errSFTPLDAPNotEnabled     = errors.New("ldap authentication is not enabled")
)

// if the sftp parameter --trusted-user-ca-key is set, then
// the final form of the key file will be set as this variable.
var caPublicKey ssh.PublicKey

// https://cs.opensource.google/go/x/crypto/+/refs/tags/v0.22.0:ssh/common.go;l=46
// preferredKexAlgos specifies the default preference for key-exchange

}

type restError string

func (e restError) Error() string {
	return string(e)
}

func (e restError) Timeout() bool {
	return true
}

// Given a string of the form "host", "host:port", or "[ipv6::address]:port",
// return true if the string includes a port.
func hasPort(s string) bool { return strings.LastIndex(s, ":") > strings.LastIndex(s, "]") }

	ErrPastObjectLockRetainDate = errors.New("the retain until date must be in the future")
	// ErrUnknownWORMModeDirective - indicates that the retention mode is invalid
	ErrUnknownWORMModeDirective = errors.New("unknown WORM mode directive")
	// ErrObjectLockMissingContentMD5 - indicates missing Content-MD5 header for put object requests with locking

    val alternative: MediaType = MultipartBody.ALTERNATIVE
    val digest: MediaType = MultipartBody.DIGEST
    val parallel: MediaType = MultipartBody.PARALLEL
    val form: MediaType = MultipartBody.FORM
  }

  @Test
  fun multipartBodyPart() {
    val requestBody: RequestBody = "".toRequestBody(null)
    var part: MultipartBody.Part = MultipartBody.Part.create(null, requestBody)

      throws IOException {
    // Interestingly, unlike File.getCanonicalFile(), Path/Files provides no way of getting the
    // canonical (absolute, normalized, symlinks resolved, etc.) form of a path to a nonexistent
    // file. getCanonicalFile() can at least get the canonical form of the part of the path which
    // actually exists and then append the normalized remainder of the path to that.
    Path normalizedAbsolutePath = path.toAbsolutePath().normalize();

      throws IOException {
    // Interestingly, unlike File.getCanonicalFile(), Path/Files provides no way of getting the
    // canonical (absolute, normalized, symlinks resolved, etc.) form of a path to a nonexistent
    // file. getCanonicalFile() can at least get the canonical form of the part of the path which
    // actually exists and then append the normalized remainder of the path to that.
    Path normalizedAbsolutePath = path.toAbsolutePath().normalize();

Esto incluye a librerías externas basadas en Pydantic como <abbr title="Object-Relational Mapper">ORM</abbr>s y <abbr title="Object-Document Mapper">ODM</abbr>s para bases de datos.

### 步骤 5：返回内容

```Python hl_lines="8"
{!../../docs_src/first_steps/tutorial001.py!}
```

你可以返回一个 `dict`、`list`，像 `str`、`int` 一样的单个值，等等。

你还可以返回 Pydantic 模型（稍后你将了解更多）。

还有许多其他将会自动转换为 JSON 的对象和模型（包括 ORM 对象等）。尝试下使用你最喜欢的一种，它很有可能已经被支持。

## 总结

* 导入 `FastAPI`。
* 创建一个 `app` 实例。
* 编写一个**路径操作装饰器**（如 `@app.get("/")`）。
* 编写一个**路径操作函数**（如上面的 `def root(): ...`）。