与在*路径操作函数*中使用 `Query`、`Path` 、`Body` 声明校验与元数据的方式一样，可以使用 Pydantic 的 `Field` 在 Pydantic 模型内部声明校验和元数据。

## 导入 `Field`

首先，从 Pydantic 中导入 `Field`：

=== "Python 3.10+"

    ```Python hl_lines="4"
    {!> ../../../docs_src/body_fields/tutorial001_an_py310.py!}
    ```

=== "Python 3.9+"

    ```Python hl_lines="4"
    {!> ../../../docs_src/body_fields/tutorial001_an_py39.py!}
    ```

=== "Python 3.8+"

    ```

!!! warning "경고"
    `Field`는 다른 것들처럼 (`Query`, `Path`, `Body` 등) `fastapi`에서가 아닌 `pydantic`에서 바로 임포트 되는 점에 주의하세요.

## 모델 어트리뷰트 선언

그 다음 모델 어트리뷰트와 함께 `Field`를 사용할 수 있습니다:

=== "Python 3.10+"

    ```Python hl_lines="11-14"
    {!> ../../../docs_src/body_fields/tutorial001_an_py310.py!}
    ```

=== "Python 3.9+"

    ```Python hl_lines="11-14"

  // APIVersion field. It is necessary to track the version of a field
  // set because it cannot be automatically converted.
  optional string apiVersion = 3;

  // Time is the timestamp of when the ManagedFields entry was added. The
  // timestamp will also be updated if a field is added, the manager
  // changes any of the owned fields value or removes a field. The
  // timestamp does not update when a field is removed from the entry

  // It is machine-readable.
  // This field cannot be empty for new Events.
  optional string type = 11;

  // deprecatedSource is the deprecated field assuring backward compatibility with core.v1 Event type.
  // +optional
  optional k8s.io.api.core.v1.EventSource deprecatedSource = 12;

  // deprecatedFirstTimestamp is the deprecated field assuring backward compatibility with core.v1 Event type.
  // +optional

  // This field is set via the /status subresource. Once populated, this field is immutable.
  //
  // If the certificate signing request is denied, a condition of type "Denied" is added and this field remains empty.
  // If the signer cannot issue the certificate, a condition of type "Failed" is added and this field remains empty.
  //
  // Validation requirements:

  // must be given precedence over this field. The controller may emit a
  // warning if the field and annotation have different values.
  // Implementations of this API should ignore Ingresses without a class
  // specified. An IngressClass resource may be marked as default, which can
  // be used to set a default value for this field. For more information,
  // refer to the IngressClass documentation.

  // Other drivers can leave pod info disabled and/or ignore this field.
  // As Kubernetes 1.15 doesn't support this field, drivers can only support one mode when
  // deployed on such a cluster and the deployment determines which mode that is, for example
  // via a command line parameter of the driver.
  //
  // This field is immutable.
  //
  // +optional
  optional bool podInfoOnMount = 2;

   * remain in flight.
   */
  var maxRequests = 64
    get() = this.withLock { field }
    set(maxRequests) {
      require(maxRequests >= 1) { "max < 1: $maxRequests" }
      this.withLock {
        field = maxRequests
      }
      promoteAndExecute()
    }

  /**

  // service; otherwise creation of the service will fail. This field may not
  // be changed through updates unless the type field is also being changed
  // to ExternalName (which requires this field to be blank) or the type
  // field is being changed from ExternalName (in which case this field may
  // optionally be specified, as describe above).  Valid values are "None",

  // honor this field as long as the requested duration is not greater than the
  // maximum duration they will honor per the --cluster-signing-duration CLI
  // flag to the Kubernetes controller manager.
  //
  // Certificate signers may not honor this field for various reasons:
  //
  //   1. Old signer that is unaware of the field (such as the in-tree
  //      implementations prior to v1.22)