/**
 * A sorted set which forwards all its method calls to another sorted set. Subclasses should
 * override one or more methods to modify the behavior of the backing sorted set as desired per the
 * <a href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *
 * <p><b>Warning:</b> The methods of {@code ForwardingSortedSet} forward <i>indiscriminately</i> to

/**
 * A mutable class-to-instance map backed by an arbitrary user-provided map. See also {@link
 * ImmutableClassToInstanceMap}.
 *
 * <p>See the Guava User Guide article on <a href=
 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#classtoinstancemap">{@code
 * ClassToInstanceMap}</a>.
 *
 * @author Kevin Bourrillion
 * @since 2.0
 */
@J2ktIncompatible
@GwtIncompatible

/**
 * A {@link Graph} whose elements and structural relationships will never change. Instances of this
 * class may be obtained with {@link #copyOf(Graph)}.
 *
 * <p>See the Guava User's Guide's <a
 * href="https://github.com/google/guava/wiki/GraphsExplained#immutable-implementations">discussion
 * of the {@code Immutable*} types</a> for more information on the properties and guarantees
 * provided by this class.
 *

        return append(System.lineSeparator());
    }

    /**
     * Append formatted content to the buffer.
     * @see String#format(String, Object...)
     *
     * @param pattern a <a href="../util/Formatter.html#syntax">format string</a>
     * @param args arguments referenced by the format specifiers in the format string
     * @return the current builder
     */
    @Nonnull

```Python
from .routers import items, users
```

The second version is an "absolute import":

```Python
from app.routers import items, users
```

To learn more about Python Packages and Modules, read <a href="https://docs.python.org/3/tutorial/modules.html" class="external-link" target="_blank">the official Python documentation about Modules</a>.

///

### Avoid name collisions

一个不太明显而又特别的优势是，你可以为你的API针对不同的**编程语言**来**生成客户端**(有时候被叫做 <abbr title="Software Development Kits">**SDKs**</abbr> )。

## OpenAPI 客户端生成

有许多工具可以从**OpenAPI**生成客户端。

一个常见的工具是 <a href="https://openapi-generator.tech/" class="external-link" target="_blank">OpenAPI Generator</a>。

如果您正在开发**前端**，一个非常有趣的替代方案是 <a href="https://github.com/hey-api/openapi-ts" class="external-link" target="_blank">openapi-ts</a>。

## 生成一个 TypeScript 前端客户端

让我们从一个简单的 FastAPI 应用开始：

有另一种方法可以显式的声明一个值是必需的，即将默认参数的默认值设为 `...` ：

```Python hl_lines="7"
{!../../docs_src/query_params_str_validations/tutorial006b.py!}
```

/// info

如果你之前没见过 `...` 这种用法：它是一个特殊的单独值，它是 <a href="https://docs.python.org/3/library/constants.html#Ellipsis" class="external-link" target="_blank">Python 的一部分并且被称为「省略号」</a>。
Pydantic 和 FastAPI 使用它来显式的声明需要一个值。

///

这将使 **FastAPI** 知道此查询参数是必需的。

 * class be used, at a small efficiency penalty, to enforce the distinction in the type system.
 *
 * <p>See the Guava User Guide article on <a
 * href="https://github.com/google/guava/wiki/PrimitivesExplained#unsigned-support">unsigned
 * primitive utilities</a>.
 *
 * @author Louis Wasserman
 * @since 11.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault

 * class be used, at a small efficiency penalty, to enforce the distinction in the type system.
 *
 * <p>See the Guava User Guide article on <a
 * href="https://github.com/google/guava/wiki/PrimitivesExplained#unsigned-support">unsigned
 * primitive utilities</a>.
 *
 * @author Louis Wasserman
 * @since 11.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault

/**
 * A list which forwards all its method calls to another list. Subclasses should override one or
 * more methods to modify the behavior of the backing list as desired per the <a
 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *
 * <p>This class does not implement {@link java.util.RandomAccess}. If the delegate supports random