With an ORM, you normally create a class that represents a table in a SQL database, each attribute of the class represents a column, with a name and a type.

For example a class `Pet` could represent a SQL table `pets`.

And each *instance* object of that class represents a row in the database.

## ORMs（对象关系映射）

**FastAPI**可与任何数据库在任何样式的库中一起与 数据库进行通信。

一种常见的模式是使用“ORM”：对象关系映射。

ORM 具有在代码和数据库表（“*关系型”）中的**对象**之间转换（“*映射*”）的工具。

使用 ORM，您通常会在 SQL 数据库中创建一个代表映射的类，该类的每个属性代表一个列，具有名称和类型。

例如，一个类`Pet`可以表示一个 SQL 表`pets`。

该类的每个*实例对象都代表数据库中的一行数据。*

又例如，一个对象`orion_cat`（`Pet`的一个实例）可以有一个属性`orion_cat.type`, 对标数据库中的`type`列。并且该属性的值可以是其它，例如`"cat"`。

这些 ORM 还具有在表或实体之间建立关系的工具（比如创建多表关系）。

**FastAPI** 👷 ⏮️ 🙆 💽 & 🙆 👗 🗃 💬 💽.

⚠ ⚓ ⚙️ "🐜": "🎚-🔗 🗺" 🗃.

🐜 ✔️ 🧰 🗜 ("*🗺*") 🖖 *🎚* 📟 & 💽 🏓 ("*🔗*").

⏮️ 🐜, 👆 🛎 ✍ 🎓 👈 🎨 🏓 🗄 💽, 🔠 🔢 🎓 🎨 🏓, ⏮️ 📛 & 🆎.

🖼 🎓 `Pet` 💪 🎨 🗄 🏓 `pets`.

& 🔠 *👐* 🎚 👈 🎓 🎨 ⏭ 💽.

🖼 🎚 `orion_cat` (👐 `Pet`) 💪 ✔️ 🔢 `orion_cat.type`, 🏓 `type`. & 💲 👈 🔢 💪, ✅ `"cat"`.

👫 🐜 ✔️ 🧰 ⚒ 🔗 ⚖️ 🔗 🖖 🏓 ⚖️ 👨‍💼.

   * It is set by a client who only wants to make a request if it can be fully satisfied by the
   * cache. Cached responses that would require validation (ie. conditional gets) are not permitted
   * if this header is set.
   */
  @get:JvmName("onlyIfCached") val onlyIfCached: Boolean,
  @get:JvmName("noTransform") val noTransform: Boolean,
  @get:JvmName("immutable") val immutable: Boolean,

        - If so, calls `istio-iptables` with params to setup pod netns
        - If ambient, sets up the ambient logic.

- `istio-iptables`
    - sets up iptables to redirect a list of ports to the port envoy will listen
    - shared code with istio-init container

      }

    /**
     * Sets the URL target of this request.
     *
     * @throws IllegalArgumentException if [url] is not a valid HTTP or HTTPS URL. Avoid this
     *     exception by calling [HttpUrl.parse]; it returns null for invalid URLs.
     */
    open fun url(url: String): Builder {
      return url(canonicalUrl(url).toHttpUrl())
    }

    /**
     * Sets the URL target of this request.
     *

    }
  }

  /**
   * This test reproduces a crash where OkHttp attempted to use a deferred connection when the call
   * already had a healthy connection. It sets up a deferred connection by stalling the IPv6
   * connect, and it sets up a same-connection retry with [ErrorCode.REFUSED_STREAM].
   *
   * https://github.com/square/okhttp/pull/7190
   */
  @Test
  fun preferCallConnectionOverDeferredConnection() {

    change.
-   You make the change and submit it for the review again.
-   This cycle repeats itself until the PR gets approved.
-   Note: As a friendly reminder, we may reach out to you if the PR is awaiting
    your response for more than 2 weeks.

**4. Approved**

-   Once the PR is approved, it gets `kokoro:force-run` label applied and it
    initiates CI/CD tests.
-   We can't move forward if these tests fail.

  optional string message = 5;
}

// DaemonSetList is a collection of daemon sets.
message DaemonSetList {
  // Standard list metadata.
  // More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#metadata
  // +optional
  optional k8s.io.apimachinery.pkg.apis.meta.v1.ListMeta metadata = 1;

  // A list of daemon sets.
  repeated DaemonSet items = 2;
}

   * SET types.
   *
   * The fields are specified as a list of member adapters. When decoding, a value for each
   * non-optional member but be included in sequence.
   *
   * TODO: for sets, sort by tag when encoding.
   * TODO: for set ofs, sort by encoded value when encoding.
   */
  fun <T> sequence(
    name: String,
    vararg members: DerAdapter<*>,
    decompose: (T) -> List<*>,