public void testNoExceptionsThrown() throws IOException {
    Closer closer = new Closer(suppressor);

    TestCloseable c1 = closer.register(TestCloseable.normal());
    TestCloseable c2 = closer.register(TestCloseable.normal());
    TestCloseable c3 = closer.register(TestCloseable.normal());

    assertFalse(c1.isClosed());
    assertFalse(c2.isClosed());
    assertFalse(c3.isClosed());

    closer.close();

# Extending OpenAPI { #extending-openapi }

There are some cases where you might need to modify the generated OpenAPI schema.

In this section you will see how.

## The normal process { #the-normal-process }

The normal (default) process, is as follows.

A `FastAPI` application (instance) has an `.openapi()` method that is expected to return the OpenAPI schema.

  public void testNoExceptionsThrown() throws IOException {
    Closer closer = new Closer(suppressor);

    TestCloseable c1 = closer.register(TestCloseable.normal());
    TestCloseable c2 = closer.register(TestCloseable.normal());
    TestCloseable c3 = closer.register(TestCloseable.normal());

    assertFalse(c1.isClosed());
    assertFalse(c2.isClosed());
    assertFalse(c3.isClosed());

    closer.close();

### Raise exceptions { #raise-exceptions }

These dependencies can `raise` exceptions, the same as normal dependencies:

{* ../../docs_src/dependencies/tutorial006_an_py39.py hl[10,15] *}

### Return values { #return-values }

And they can return values or not, the values won't be used.

    }
  }

  @Test
  fun upgradesOnReusedConnection() {
    server.enqueue(MockResponse(body = "normal request"))
    client.newCall(Request(server.url("/"))).execute().use { response ->
      assertThat(response.body.string()).isEqualTo("normal request")
    }

    upgrade()

    assertThat(server.takeRequest().connectionIndex).isEqualTo(0)

## The normal **FastAPI** app { #the-normal-fastapi-app }

Let's first see how the normal API app would look like before adding the callback.

It will have a *path operation* that will receive an `Invoice` body, and a query parameter `callback_url` that will contain the URL for the callback.

This part is pretty normal, most of the code is probably already familiar to you:

### Outras funções de utilidade

Qualquer outra função de utilidade que você chame diretamente pode ser criada com `def` normal ou `async def` e o FastAPI não irá afetar o modo como você a chama.

### Diğer yardımcı fonksiyonlar

Doğrudan çağırdığınız diğer herhangi bir yardımcı fonksiyonu, normal "def" veya "async def" ile tanimlayabilirsiniz. FastAPI onu çağırma şeklinizi etkilemez.

### Otras funciones de utilidad

Cualquier otra función de utilidad que llames directamente puede ser creada con `def` normal o `async def` y FastAPI no afectará la forma en que la llames.

There are cases where you want to tell your API **users** that your app could call *their* app (sending a request) with some data, normally to **notify** of some type of **event**.

This means that instead of the normal process of your users sending requests to your API, it's **your API** (or your app) that could **send requests to their system** (to their API, their app).

This is normally called a **webhook**.