* provide much stronger guarantees.
 *
 * <h3>Comparison to a map of collections</h3>
 *
 * <p>Multimaps are commonly used in places where a {@code Map<K, Collection<V>>} would otherwise
 * have appeared. The differences include:
 *
 * <ul>
 *   <li>There is no need to populate an empty collection before adding an entry with {@link #put
 *       put}.

* Then **comment** saying that you did that, that's how I will know you really checked it.

/// info

Unfortunately, I can't simply trust PRs that just have several approvals.

Several times it has happened that there are PRs with 3, 5 or more approvals, probably because the description is appealing, but when I check the PRs, they are actually broken, have a bug, or don't solve the problem they claim to solve. 😅

   * <p>The returned set has an iterator that does not support {@code remove()}.
   *
   * <p>The set's iterator traverses the columns of the first row, the columns of the second row,
   * etc., skipping any columns that have appeared previously.
   */
  @Override
  public Set<C> columnKeySet() {
    Set<C> result = columnKeySet;
    return (result == null) ? columnKeySet = new ColumnKeySet() : result;
  }

  @WeakOuter

        return new SimpleBuildEventListener(writer);
    }

    protected final void createTerminal(C context) {
        if (context.terminal == null) {
            // Create the build log appender; also sets MavenSimpleLogger sink
            ProjectBuildLogAppender projectBuildLogAppender =
                    new ProjectBuildLogAppender(determineBuildEventListener(context));

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

La segunda versión es un "import absoluto":

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

Para aprender más sobre Paquetes y Módulos de Python, lee [la documentación oficial de Python sobre Módulos](https://docs.python.org/3/tutorial/modules.html).

///

### Evitar colisiones de nombres { #avoid-name-collisions }

Al configurar `--proxy-headers` ahora FastAPI podrá redirigir a la ubicación correcta. 😎

```
https://mysuperapp.com/items/
```

/// tip | Consejo

Si quieres aprender más sobre HTTPS, revisa la guía [Acerca de HTTPS](../deployment/https.md).

///

### Cómo funcionan los headers reenviados por el Proxy { #how-proxy-forwarded-headers-work }

    computationComplete.await();

    // At this point, the listener should be holding the seed value (a -> a), and the map should
    // contain the computed value (b -> b), since the clear() happened before the computation
    // completed.
    assertThat(listener).hasSize(1);
    RemovalNotification<String, String> notification = listener.remove();
    assertThat(notification.getKey()).isEqualTo("a");

    computationComplete.await();

    // At this point, the listener should be holding the seed value (a -> a), and the map should
    // contain the computed value (b -> b), since the clear() happened before the computation
    // completed.
    assertThat(listener).hasSize(1);
    RemovalNotification<String, String> notification = listener.remove();
    assertThat(notification.getKey()).isEqualTo("a");

* `max_length`
* `pattern`

Validaciones personalizadas usando `AfterValidator`.

En estos ejemplos viste cómo declarar validaciones para valores de tipo `str`.

   * <p>The returned set has an iterator that does not support {@code remove()}.
   *
   * <p>The set's iterator traverses the columns of the first row, the columns of the second row,
   * etc., skipping any columns that have appeared previously.
   */
  @Override
  public Set<C> columnKeySet() {
    Set<C> result = columnKeySet;
    return (result == null) ? columnKeySet = new ColumnKeySet() : result;
  }

  @WeakOuter