## Usando `BackgroundTasks` { #using-backgroundtasks }

Primeiro, importe `BackgroundTasks` e defina um parâmetro na sua *função de operação de rota* com uma declaração de tipo `BackgroundTasks`:

{* ../../docs_src/background_tasks/tutorial001_py39.py hl[1,13] *}

O **FastAPI** criará o objeto do tipo `BackgroundTasks` para você e o passará como esse parâmetro.

## Crie uma função de tarefa { #create-a-task-function }

            assertHasErrors(
                "Field nonFinalField: Nullability breaking change.",
                "Method com.example.Source.foo(java.lang.String): Parameter 0 from null accepting to non-null accepting breaking change.",
                "Constructor com.example.Source(java.lang.String): Parameter 0 from null accepting to non-null accepting breaking change."
            )
            assertHasNoWarning()
            assertHasNoInformation()
        }

            data = websocket.receive_text()
            assert data == "Session cookie or query token value is: some-token"
            data = websocket.receive_text()
            assert data == "Query parameter q is: 3"
            data = websocket.receive_text()
            assert data == f"Message text was: {message}, for item ID: 2"
            message = "Message two"
            websocket.send_text(message)

def test_query_pass_extra_list():
    client = TestClient(app)
    resp = client.get(
        "/query",
        params={
            "param": "123",
            "param2": ["456", "789"],  # Pass a list of values as extra parameter
        },
    )
    assert resp.status_code == 200
    assert resp.json() == {
        "param": "123",
        "param2": ["456", "789"],
    }


def test_query_pass_extra_single():

          | RuntimeException
          | Error t) { // ensure we really catch *everything*
        return weakSetValidator();
      }
    }
  }

  // TODO(cpovirk): change parameter order to match other helper methods (Class, Throwable)?
  private static <X extends Exception> void wrapAndThrowExceptionOrError(
      Throwable cause, Class<X> exceptionClass) throws X {
    if (cause instanceof Error) {

...ele possui os mesmos parâmetros que nosso `common_parameters` anterior:

{* ../../docs_src/dependencies/tutorial001_an_py310.py hl[8] *}

Esses parâmetros são utilizados pelo **FastAPI** para "definir" a dependência.

Em ambos os casos teremos:

* Um parâmetro de consulta `q` opcional do tipo `str`.
* Um parâmetro de consulta `skip` do tipo `int`, com valor padrão `0`.

     * other SMB clients (including other threads making calls into jCIFS)
     * will not be permitted to access the target file and will receive "The
     * file is being accessed by another process" message.
     */
    int FILE_NO_SHARE = 0x00;
    /**
     * When specified as the <code>shareAccess</code> constructor parameter,

In this case, this `__call__` is what **FastAPI** will use to check for additional parameters and sub-dependencies, and this is what will be called to pass a value to the parameter in your *path operation function* later.

## Parameterize the instance { #parameterize-the-instance }

And now, we can use `__init__` to declare the parameters of the instance that we can use to "parameterize" the dependency:

Betrachten wir die deklarierten Parameter:

* Obwohl diese Funktion selbst eine Abhängigkeit ist („Dependable“, etwas hängt von ihr ab), deklariert sie auch eine andere Abhängigkeit („Dependant“, sie hängt von etwas anderem ab).
    * Sie hängt von `query_extractor` ab und weist den von diesem zurückgegebenen Wert dem Parameter `q` zu.
* Sie deklariert außerdem ein optionales `last_query`-Cookie, ein `str`.

      <version>1.0.0</version>
      <name>ExpressionDocumentation</name>
      <description>The root of a parameter plugin expression document.</description>
      <fields>
        <field>
          <version>1.0.0</version>
          <name>expressions</name>
          <description>The list of plugin parameter expressions described by this
            document.</description>
          <association>