{*../../docs_src/websockets/tutorial003_py39.py hl[79:81]*}

Para testar:

* Abrar o aplicativo com várias abas do navegador.
* Escreva mensagens a partir delas.
* Então feche uma das abas.

Isso levantará a exceção `WebSocketDisconnect`, e todos os outros clientes receberão uma mensagem como:

```
Client #1596980209979 left the chat
```

/// tip | Dica

sterås","mörbylånga","nacka","nora","norberg","nordanstig","nordmaling","norrköping","norrtälje","norsjö","nybro","nykvarn","nyköping","nynäshamn","nässjö","ockelbo","olofström","orsa","orust","osby","oskarshamn","ovanåker","oxelösund","pajala","partille","perstorp","piteå","ragunda","robertsfors","ronneby","rättvik","sala","salem","sandviken","sigtuna","simrishamn","sjöbo","skara","skellefteå","skinnskatteberg","skurup","skövde","smedjebacken","sollefteå","sollentuna","solna","sorsele","sotenäs...

    /**
     * Returns {@code true} if the value has been partially collected, meaning that the value is
     * null.
     */
    static <K, V, E extends InternalEntry<K, V, E>> boolean isCollected(E entry) {
      return entry.getValue() == null;
    }

    /**
     * Gets the value from an entry. Returns {@code null} if the entry is invalid or
     * partially-collected.
     */
    @CheckForNull

Dans ce cadre, j'ai dû étudier, tester et utiliser de nombreuses alternatives.

L'histoire de **FastAPI** est en grande partie l'histoire de ses prédécesseurs.

Comme dit dans la section [Alternatives](alternatives.md){.internal-link target=\_blank} :

<blockquote markdown="1">

    <magic priority="50">
      <match value="Article" type="string" offset="0" />
    </magic>
    <sub-class-of type="text/x-tika-text-based-message"/>
  </mime-type>

  <mime-type type="message/partial"/>

  <mime-type type="message/rfc822">
    <magic priority="50">
      <!-- these should be 100% hits...if you see this at offset=0 -->
      <match value="Relay-Version:" type="stringignorecase" offset="0"/>

	CopyObjectPart(ctx context.Context, srcBucket, srcObject, destBucket, destObject string, uploadID string, partID int,
		startOffset int64, length int64, srcInfo ObjectInfo, srcOpts, dstOpts ObjectOptions) (info PartInfo, err error)
	PutObjectPart(ctx context.Context, bucket, object, uploadID string, partID int, data *PutObjReader, opts ObjectOptions) (info PartInfo, err error)

    /**
     * Returns {@code true} if the value has been partially collected, meaning that the value is
     * null.
     */
    static <K, V, E extends InternalEntry<K, V, E>> boolean isCollected(E entry) {
      return entry.getValue() == null;
    }

    /**
     * Gets the value from an entry. Returns {@code null} if the entry is invalid or
     * partially-collected.
     */
    @CheckForNull

   *     {@code get()} throws a different kind of exception, that exception itself.
   * @param executor the executor that runs {@code fallback} if the input fails
   */
  @J2ktIncompatible
  @Partially.GwtIncompatible("AVAILABLE but requires exceptionType to be Throwable.class")
  public final <X extends Throwable> FluentFuture<V> catching(
      Class<X> exceptionType, Function<? super X, ? extends V> fallback, Executor executor) {

                                "schema": {}
                            }
                        }
                    }
                },
                "x-aperture-labs-portal": "blue"
            }
        }
    }
}
```

### 🛃 🗄 *➡ 🛠️* 🔗

📖 `openapi_extra` 🔜 🙇 🔗 ⏮️ 🔁 🏗 🗄 🔗 *➡ 🛠️*.

, 👆 💪 🚮 🌖 💽 🔁 🏗 🔗.

Portanto, o navegador irá enviar uma requisição HTTP `OPTIONS` ao backend, e se o backend enviar os cabeçalhos apropriados autorizando a comunicação a partir de uma origem diferente (`http://localhost:8080`) então o navegador deixará o JavaScript no frontend enviar sua requisição para o backend.

Para conseguir isso, o backend deve ter uma lista de "origens permitidas".