Object key = new Object();
    assertThat(cache.getUnchecked(key)).isSameInstanceAs(computed);
    RemovalNotification<Object, Object> notification = listener.remove();
    assertThat(notification.getKey()).isSameInstanceAs(key);
    assertThat(notification.getValue()).isSameInstanceAs(computed);
    assertThat(notification.getCause()).isEqualTo(RemovalCause.SIZE);
    assertThat(listener.isEmpty()).isTrue();
    checkEmpty(cache);
  }

    Object key = new Object();
    assertThat(cache.getUnchecked(key)).isSameInstanceAs(computed);
    RemovalNotification<Object, Object> notification = listener.remove();
    assertThat(notification.getKey()).isSameInstanceAs(key);
    assertThat(notification.getValue()).isSameInstanceAs(computed);
    assertThat(notification.getCause()).isEqualTo(RemovalCause.SIZE);
    assertThat(listener.isEmpty()).isTrue();
    checkEmpty(cache);
  }

    // Verify that each received removal notification was valid
    for (RemovalNotification<String, String> notification : removalListener) {
      assertWithMessage("Invalid removal notification")
          .that(notification.getValue())
          .isEqualTo(notification.getKey());
    }

    CacheStats stats = cache.stats();

    if log.is_file():
        os.remove(log)  # pragma: no cover
    response = client.post("/send-notification/******@****.***")
    assert response.status_code == 200, response.text
    assert response.json() == {"message": "Notification sent in the background"}
    with open("./log.txt") as f:

    with open("log.txt", mode="w") as email_file:
        content = f"notification for {email}: {message}"
        email_file.write(content)


@app.post("/send-notification/{email}")
async def send_notification(email: str, background_tasks: BackgroundTasks):
    background_tasks.add_task(write_notification, email, message="some notification")

    * Collect the money from the client.
    * Send a notification back to the API user (the external developer), as a callback.
        * At this point is that the API will somehow send a POST request to the
            external API with the notification of the invoice event
            (e.g. "payment successful").
    """
    # Send the invoice, collect the money, send the notification (the callback)
    return {"msg": "Invoice received"}

    List<RemovalNotification<Integer, Integer>> notifications = new ArrayList<>();
    Cache<Integer, Integer> cache =
        CacheBuilder.newBuilder()
            .removalListener(
                new RemovalListener<Integer, Integer>() {
                  @Override
                  public void onRemoval(RemovalNotification<Integer, Integer> notification) {
                    notifications.add(notification);
                  }

    * Collect the money from the client.
    * Send a notification back to the API user (the external developer), as a callback.
        * At this point is that the API will somehow send a POST request to the
            external API with the notification of the invoice event
            (e.g. "payment successful").
    """
    # Send the invoice, collect the money, send the notification (the callback)

            content = f"notification for {email}: {message}"
            email_file.write(content)


    @app.post("/send-notification/{email}")
    async def send_notification(email: str, background_tasks: BackgroundTasks):
        background_tasks.add_task(write_notification, email, message="some notification")
        return {"message": "Notification sent in the background"}
    ```
    """

    * Collect the money from the client.
    * Send a notification back to the API user (the external developer), as a callback.
        * At this point is that the API will somehow send a POST request to the
            external API with the notification of the invoice event
            (e.g. "payment successful").
    """
    # Send the invoice, collect the money, send the notification (the callback)