但是一旦我们创建了一个`SessionLocal`类的实例，这个实例将是实际的数据库会话。

我们将它命名为`SessionLocal`是为了将它与我们从 SQLAlchemy 导入的`Session`区别开来。

稍后我们将使用`Session`（从 SQLAlchemy 导入的那个）。

要创建`SessionLocal`类，请使用函数`sessionmaker`：

```Python hl_lines="11"
{!../../docs_src/sql_databases/sql_app/database.py!}
```

### 创建一个`Base`类

现在我们将使用`declarative_base()`返回一个类。

稍后我们将继承这个类，来创建每个数据库模型或类（ORM 模型）：

```Python hl_lines="13"

  v. rights protecting the extraction, dissemination, use and reuse of data
     in a Work;
 vi. database rights (such as those arising under Directive 96/9/EC of the
     European Parliament and of the Council of 11 March 1996 on the legal
     protection of databases, and under any national implementation
     thereof, including any amended or successor version of such
     directive); and

- [v1.10.2](#v1102)
  - [Downloads for v1.10.2](#downloads-for-v1102)
    - [Client Binaries](#client-binaries-11)
    - [Server Binaries](#server-binaries-11)
    - [Node Binaries](#node-binaries-11)
  - [Changelog since v1.10.1](#changelog-since-v1101)
    - [Other notable changes](#other-notable-changes-11)
- [v1.10.1](#v1101)
  - [Downloads for v1.10.1](#downloads-for-v1101)
    - [Client Binaries](#client-binaries-12)

    - [Other notable changes](#other-notable-changes-9)
- [v1.13.1](#v1131)
  - [Downloads for v1.13.1](#downloads-for-v1131)
    - [Client Binaries](#client-binaries-11)
    - [Server Binaries](#server-binaries-11)
    - [Node Binaries](#node-binaries-11)
  - [Changelog since v1.13.0](#changelog-since-v1130)
    - [Other notable changes](#other-notable-changes-10)
- [v1.13.0](#v1130)
  - [Downloads for v1.13.0](#downloads-for-v1130)

For example, given the function:
</p>

<pre>
func f[P ~float32|~float64]() {
	… P(1.1) …
}
</pre>

<p>
the conversion <code>P(1.1)</code> results in a non-constant value of type <code>P</code>
and the value <code>1.1</code> is represented as a <code>float32</code> or a <code>float64</code>
depending on the type argument for <code>f</code>.

  - [External Dependencies](#external-dependencies)
- [v1.14.0-rc.1](#v1140-rc1)
  - [Downloads for v1.14.0-rc.1](#downloads-for-v1140-rc1)
    - [Client Binaries](#client-binaries-11)
    - [Server Binaries](#server-binaries-11)
    - [Node Binaries](#node-binaries-11)
  - [Changelog since v1.14.0-beta.2](#changelog-since-v1140-beta2)
    - [Action Required](#action-required)
    - [Other notable changes](#other-notable-changes-9)

    public static final String CONSTRAINTS_Mod10Check_MESSAGE = "{constraints.Mod10Check.message}";

    /** The key of the message: The check digit for ${value} is invalid, Modulo 11 checksum failed. */
    public static final String CONSTRAINTS_Mod11Check_MESSAGE = "{constraints.Mod11Check.message}";

    /** The key of the message: The check digit for ${value} is invalid, ${modType} checksum failed. */

      // the U/L and G bits, with which we are not concerned.
      return false;
    }

    return (bytes[9] == (byte) 0x00) && (bytes[10] == (byte) 0x5e) && (bytes[11] == (byte) 0xfe);
  }

  /**
   * Returns the IPv4 address embedded in an ISATAP address.
   *
   * @param ip {@link Inet6Address} to be examined for embedded IPv4 in ISATAP address

   * double-width).
   *
   * <p><b>Note:</b> as the reference file evolves, we will modify this matcher to keep it up to
   * date.
   *
   * <p>See also <a href="http://www.unicode.org/reports/tr11/">UAX #11 East Asian Width</a>.
   *
   * @deprecated Many such characters are supplementary characters; see the class documentation.
   * @since 19.0 (since 1.0 as constant {@code SINGLE_WIDTH})
   */
  @Deprecated

			disks := er.getDisks()
			distribution := hashOrder(pathJoin(bucket, object), nDisks)
			shuffledDisks := shuffleDisks(disks, distribution)

			// remove last data shard
			err = removeAll(pathJoin(shuffledDisks[11].String(), bucket, object))
			if err != nil {
				t.Fatalf("Failed to delete a file - %v", err)
			}
			_, err = obj.HealObject(ctx, bucket, object, "", madmin.HealOpts{
				ScanMode: madmin.HealNormalScan,