require(utf8.readByte() == '.'.code.toByte())
      val vN = utf8.readDecimalLong()
      writeVariableLengthLong(vN)
    }
  }

  fun writeRelativeObjectIdentifier(s: String) {
    // Add a leading dot so each subidentifier has a dot prefix.
    val utf8 =
      Buffer()
        .writeByte('.'.code.toByte().toInt())
        .writeUtf8(s)

    while (!utf8.exhausted()) {

   * however, {@code asMap().get(Object)} returns {@code null} instead of an empty collection.
   *
   * <p>Though the method signature doesn't say so explicitly, the returned map has {@link
   * SortedSet} values.
   */
  @Override
  public Map<K, Collection<V>> asMap() {
    return super.asMap();
  }

  /**
   * {@inheritDoc}
   *

    // The initial state corresponds to the ASCII string "somepseudorandomlygeneratedbytes",
    // big-endian encoded. There is nothing special about this value; the only requirement
    // was some asymmetry so that the initial v0 and v1 differ from v2 and v3.
    private long v0 = 0x736f6d6570736575L;
    private long v1 = 0x646f72616e646f6dL;
    private long v2 = 0x6c7967656e657261L;
    private long v3 = 0x7465646279746573L;

        // fall back to copying URLs to files in the testDir == null block below
      }
    }

    if (testDir == null) {
      // testdata resources aren't file:// urls, so create a directory to store them in and then
      // copy the resources to the filesystem as needed
      testDir = createTempDir();
    }

    return testDir;
  }

## Second dependency, "dependable" and "dependant"

Then you can create another dependency function (a "dependable") that at the same time declares a dependency of its own (so it is a "dependant" too):

//// tab | Python 3.10+

```Python hl_lines="13"
{!> ../../docs_src/dependencies/tutorial005_an_py310.py!}
```

////

//// tab | Python 3.9+

```Python hl_lines="13"

///

/// check

OpenAPI specifies that each *path operation* requires a response description.

So, if you don't provide one, **FastAPI** will automatically generate one of "Successful response".

///

<img src="/img/tutorial/path-operation-configuration/image03.png">

## Deprecate a *path operation*

Mas primeiro, vamos verificar alguns pequenos conceitos.

## Está com pressa?

Se você não se importa com qualquer um desses termos e só precisa adicionar segurança com autenticação baseada em usuário e senha _agora_, pule para os próximos capítulos.

## OAuth2

OAuth2 é uma especificação que define várias formas para lidar com autenticação e autorização.

# Header-Parameter

So wie `Query`-, `Path`-, und `Cookie`-Parameter können Sie auch <abbr title='Header – Kopfzeilen, Header, Header-Felder: Schlüssel-Wert-Metadaten, die vom Client beim Request, und vom Server bei der Response gesendet werden'>Header</abbr>-Parameter definieren.

## `Header` importieren

Importieren Sie zuerst `Header`:

//// tab | Python 3.10+

```Python hl_lines="3"
{!> ../../docs_src/header_params/tutorial001_an_py310.py!}
```

Im obigen Beispiel haben sie die Defaultwerte `skip=0` und `limit=10`.

Wenn Sie also zur URL:

```
http://127.0.0.1:8000/items/
```

gehen, so ist das das gleiche wie die URL:

```
http://127.0.0.1:8000/items/?skip=0&limit=10
```

Aber wenn Sie zum Beispiel zu:

```
http://127.0.0.1:8000/items/?skip=20
```

}

func (t *Cache[T]) update(ctx context.Context) error {
	val, err := t.updateFn(ctx)
	if err != nil {
		if t.opts.ReturnLastGood && t.val.Load() != nil {
			// Keep last good value, so update
			// does not return an error.
			return nil
		}
		return err
	}

	t.val.Store(&val)
	t.lastUpdateMs.Store(time.Now().UnixMilli())
	return nil