assertThat(network.edgesConnecting(N1, N1)).isEmpty();
    assertThat(network.edgesConnecting(N1, N2)).containsExactly(E12);
  }

  @Test
  public void concurrentIteration() throws Exception {
    addEdge(1, 2, "foo");
    addEdge(3, 4, "bar");
    addEdge(5, 6, "baz");

    int threadCount = 20;
    ExecutorService executor = newFixedThreadPool(threadCount);
    CyclicBarrier barrier = new CyclicBarrier(threadCount);

    * Nếu không, client sẽ thấy một lỗi rõ ràng và hữu ích.
* Kiểm tra xem nếu có một tham số `q` trong query string (ví dụ như `http://127.0.0.1:8000/items/foo?q=somequery`) cho request `GET`.
    * Tham số `q` được định nghĩa `= None`, nó là tùy chọn.
    * Nếu không phải `None`, nó là bắt buộc (như body trong trường hợp của `PUT`).

     * the other. From the declaration syntax, the class type parameter appears first, but the call
     * syntax may show up in opposite order such as {@code new <A>Foo<B>()}.
     */
    @Override
    public final TypeVariable<?>[] getTypeParameters() {
      TypeVariable<?>[] declaredByClass = getDeclaringClass().getTypeParameters();

   *
   * {@snippet :
   * static final ImmutableTable<Integer, Character, String> SPREADSHEET =
   *     new ImmutableTable.Builder<Integer, Character, String>()
   *         .put(1, 'A', "foo")
   *         .put(1, 'B', "bar")
   *         .put(2, 'A', "baz")
   *         .buildOrThrow();
   * }
   *
   * <p>By default, the order in which cells are added to the builder determines the iteration

* Validará que el `item_id` sea del tipo `int` para requests `GET` y `PUT`.
    * Si no lo es, el cliente verá un error útil y claro.
* Comprobará si hay un parámetro de query opcional llamado `q` (como en `http://127.0.0.1:8000/items/foo?q=somequery`) para requests `GET`.
    * Como el parámetro `q` está declarado con `= None`, es opcional.
    * Sin el `None` sería requerido (como lo es el body en el caso con `PUT`).

    * Wanneer dat niet het geval is, krijgt de cliënt een nuttige, duidelijke foutmelding.
* Controleren of er een optionele query parameter is met de naam `q` (zoals in `http://127.0.0.1:8000/items/foo?q=somequery`) voor `GET` verzoeken.
    * Aangezien de `q` parameter werd gedeclareerd met `= None`, is deze optioneel.
    * Zonder de `None` declaratie zou deze verplicht zijn (net als bij de body in het geval met `PUT`).

    * Se não é validado, o cliente verá um útil, claro erro.
* Verificar se existe um parâmetro de _query_ opcional nomeado como `q` (como em `http://127.0.0.1:8000/items/foo?q=somequery`) para requisições `GET`.
    * Como o parâmetro `q` é declarado com `= None`, ele é opcional.
    * Sem o `None` ele poderia ser obrigatório (como o corpo no caso de `PUT`).

 * returned.
 *
 * <p>All default instances returned by {@link #get} are generics-safe. Clients won't get type
 * errors for using {@code get(Comparator.class)} as a {@code Comparator<Foo>}, for example.
 * Immutable empty instances are returned for collection types; {@code ""} for string; {@code 0} for
 * number types; reasonable default instance for other stateless types. For mutable types, a fresh

* Проверять, что `item_id` имеет тип `int` для запросов `GET` и `PUT`.
    * Если это не так, клиент увидит полезную чёткую ошибку.
* Проверять, есть ли необязательный параметр запроса с именем `q` (например, `http://127.0.0.1:8000/items/foo?q=somequery`) для `GET` запросов.
    * Поскольку параметр `q` объявлен с `= None`, он является необязательным.
    * Без `None` он был бы необходим (как тело в случае с `PUT`).

                closer.eventuallyClose(autoCloseable, closingExecutor);
                return "foo";
              }
            },
            executor);
    assertThat(getFinalValue(closingFuture)).isEqualTo("foo");
    waitUntilClosed(closingFuture);
    assertClosed(closeable1);
  }

  public void testStatusFuture() throws Exception {