*
 * <h3>Building a {@code Graph}</h3>
 *
 * <p>The implementation classes that {@code common.graph} provides are not public, by design. To
 * create an instance of one of the built-in implementations of {@code Graph}, use the {@link
 * GraphBuilder} class:
 *
 * {@snippet :
 * MutableGraph<Integer> graph = GraphBuilder.undirected().build();
 * }
 *

        BlockingQueue.class,
        BlockingDeque.class,
        PriorityBlockingQueue.class,
        DelayQueue.class,
        SynchronousQueue.class,
        ConcurrentMap.class,
        ConcurrentNavigableMap.class,
        AtomicReference.class,
        AtomicBoolean.class,
        AtomicInteger.class,
        AtomicLong.class,
        AtomicDouble.class);
  }

 *
 * <h3>Building a {@code ValueGraph}</h3>
 *
 * <p>The implementation classes that {@code common.graph} provides are not public, by design. To
 * create an instance of one of the built-in implementations of {@code ValueGraph}, use the {@link
 * ValueGraphBuilder} class:
 *
 * {@snippet :
 * MutableValueGraph<Integer, Double> graph = ValueGraphBuilder.directed().build();
 * }
 *

        // Node with matching CSS class
        MockNode nodeWithClass = new MockNode("div");
        nodeWithClass.addAttribute("class", "highlight");
        assertTrue(tag.matches(nodeWithClass));

        // Node with multiple classes including target
        MockNode nodeWithMultipleClasses = new MockNode("div");
        nodeWithMultipleClasses.addAttribute("class", "container highlight active");

  @Override
  @J2ktIncompatible
  @GwtIncompatible
    Object writeReplace() {
    return super.writeReplace();
  }

  // This class is never actually serialized directly, but we have to make the
  // warning go away (and suppressing would suppress for all nested classes too)
  @GwtIncompatible @J2ktIncompatible private static final long serialVersionUID = 0;

 * all elements in priority order and place them in another collection.
 *
 * <p>Operations on this class make no guarantees about the ordering of elements with equal
 * priority. If you need to enforce an ordering, you can define custom classes or comparators that
 * use a secondary key to break ties in primary priority values. For example, here is a class that
 * applies first-in-first-out tie-breaking to comparable elements. To use it, you would insert a

```Python hl_lines="1"
{!> ../../docs_src/python_types/tutorial009_py310.py!}
```

////

使用 `str | None` 而不是仅仅 `str`，可以让编辑器帮助你发现把值当成总是 `str` 的错误（实际上它也可能是 `None`）。

### 类作为类型 { #classes-as-types }

你也可以把类声明为变量的类型。

假设你有一个名为 `Person` 的类，带有 name：

{* ../../docs_src/python_types/tutorial010_py310.py hl[1:3] *}

然后你可以声明一个变量是 `Person` 类型：

 *       #toString} behavior you expect.
 *   <li>Offers useful operations beyond just {@code get} and {@code length}, so you don't have to
 *       hunt through classes like {@link Arrays} and {@link Longs} for them.
 *   <li>Supports a copy-free {@link #subArray} view, so methods that accept this type don't need to
 *       add overloads that accept start and end indexes.

 * com.google.common.base.Function, java.util.concurrent.Executor) Futures.transform} and {@link
 * Futures#catching(ListenableFuture, Class, com.google.common.base.Function,
 * java.util.concurrent.Executor) Futures.catching}.
 *
 * <p>This class implements all methods in {@code ListenableFuture}. Subclasses should provide a way
 * to set the result of the computation through the protected methods {@link #set(Object)}, {@link

  /*
   * This class is used to serialize all ImmutableSortedSet instances,
   * regardless of implementation type. It captures their "logical contents"
   * only. This is necessary to ensure that the existence of a particular
   * implementation type is an implementation detail.
   */
  @J2ktIncompatible // serialization
  private static final class SerializedForm<E> implements Serializable {