* 使用 Pydantic 模型時，你可以把資料結構分層設計，並且用 Python 的 `List` 和 `Dict` 等型別來定義。
    * 驗證器讓我們可以輕鬆地定義和檢查複雜的資料結構，並把它們轉換成 JSON Schema 進行記錄。
    * 你可以擁有深層**巢狀的 JSON** 物件，並對它們進行驗證和註釋。
* **可擴展**：
    * Pydantic 讓我們可以定義客製化的資料型別，或者你可以使用帶有 validator 裝飾器的方法來擴展模型中的驗證功能。

	PartNumber          int                 // only useful in case of GetObject/HeadObject
	CheckPrecondFn      CheckPreconditionFn // only set during GetObject/HeadObject/CopyObjectPart preconditional valuation
	EvalMetadataFn      EvalMetadataFn      // only set for retention settings, meant to be used only when updating metadata in-place.

     * If no syntax is specified, or if its length is 1 character (interpreted as a Windows drive),
     * the default is a Maven-specific variation of the {@code "glob"} pattern.
     *
     * <p>The default implementation returns an empty list, which means to apply a language-dependent pattern.

## Modelos Pydantic { #pydantic-models }

<a href="https://docs.pydantic.dev/" class="external-link" target="_blank">Pydantic</a> es un paquete de Python para realizar la validación de datos.

Declaras la "forma" de los datos como clases con atributos.

Y cada atributo tiene un tipo.

//   - http://docs.aws.amazon.com/AmazonS3/latest/API/sigv4-streaming.html
//
// returns signature, error otherwise if the signature mismatches or any other
// error while parsing and validating.
func calculateSeedSignature(r *http.Request, trailers bool) (cred auth.Credentials, signature string, region string, date time.Time, errCode APIErrorCode) {
	// Copy request.
	req := *r

	// Save authorization header.

		0, nil, s.accessKey, s.secretKey, s.signer)
	c.Assert(err, nil)
	// executing the HTTP request.
	response, err = s.client.Do(request)
	c.Assert(err, nil)
	// validating the response status code.
	c.Assert(response.StatusCode, http.StatusOK)
	// reading the response body.
	// response body is expected to have the copied content of the first uploaded object.

## オプションの依存関係

Pydantic によって使用されるもの:

- <a href="https://github.com/JoshData/python-email-validator" target="_blank"><code>email-validator</code></a> - E メールの検証

Starlette によって使用されるもの:

- <a href="https://www.python-httpx.org" target="_blank"><code>httpx</code></a> - `TestClient`を使用するために必要です。

	_, ok := supportedS3AuthTypes[aType]
	return ok
}

// setAuthMiddleware to validate authorization header for the incoming request.
func setAuthMiddleware(h http.Handler) http.Handler {
	// handler for validating incoming authorization headers.
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		tc, ok := r.Context().Value(mcontext.ContextTraceKey).(*mcontext.TraceCtxt)

		aType := getRequestAuthType(r)

			expectedError: ioutil.ErrOverread,
		},

		// Test case - 16-19.
		// Validating for success cases.

			secretKey:            credentials.SecretKey,
			expectedBucketPolicy: "",
			expectedRespStatus:   http.StatusBadRequest,
		},
	}
	// Iterating over the cases, fetching the policy and validating the response.
	for i, testCase := range testCases {
		// expected bucket policy json string.
		expectedBucketPolicyStr := fmt.Sprintf(testCase.expectedBucketPolicy, testCase.bucketName, testCase.bucketName)