```Python hl_lines="1  4"
{!../../docs_src/python_types/tutorial009.py!}
```

Usar `Optional[str]` en lugar de solo `str` te permitirá al editor ayudarte a detectar errores donde podrías estar asumiendo que un valor siempre es un `str`, cuando en realidad también podría ser `None`.

`Optional[Something]` es realmente un atajo para `Union[Something, None]`, son equivalentes.

    it may slow down the tests for not running in parallel and may cause the
    test to timeout but it could be useful when you need to execute a single
    test or more in general your filtered/selected tests have a very low
    execution time and the sharding
    [could create an overhead on the test execution](https://github.com/bazelbuild/bazel/issues/2113#issuecomment-264054799).

    }
  ],
  "refresh": "",
  "schemaVersion": 39,
  "tags": [
    "minio"
  ],
  "templating": {
    "list": [
      {
        "current": {
          "selected": false,
          "text": "All",
          "value": "$__all"
        },
        "label": "Data source",
        "name": "DS_PROMETHEUS",
        "options": [],
        "query": "prometheus",

   * (unless they were already returned).
   *
   * The iterator supports [MutableIterator.remove]. Removing a URL from the iterator evicts the
   * corresponding response from the cache. Use this to evict selected responses.
   */
  @Throws(IOException::class)
  fun urls(): MutableIterator<String> {
    return object : MutableIterator<String> {
      private val delegate: MutableIterator<DiskLruCache.Snapshot> = cache.snapshots()

- Kubeadm: add support for dry running `kubeadm...

   * declaration of a method with the same name and formal parameters as {@link Object#equals} that
   * is not public and boolean-returning, or that declares any type parameters, would be rejected at
   * compile-time.
   */
  private static boolean isEquals(Member member) {
    if (!(member instanceof Method)) {
      return false;
    }
    Method method = (Method) member;

     *     <li>"l" or "l(num)" - lowest version or bottom list of lowest ones filter</li>
     *     <li>"s" - contextual snapshot filter</li>
     *     <li>"ns" - unconditional snapshot filter (no snapshots selected from ranges)</li>
     *     <li>"e(G:A:V)" - predicate filter (leaves out G:A:V from range, if hit, V can be range)</li>
     * </ul>

```Python hl_lines="1  4"
{!../../docs_src/python_types/tutorial009.py!}
```

O uso de `Optional[str]` em vez de apenas `str` permitirá que o editor o ajude a detectar erros, onde você pode estar assumindo que um valor é sempre um `str`, quando na verdade também pode ser `None`.

`Optional[Something]` é na verdade um atalho para `Union[Something, None]`, eles são equivalentes.

		Help:      "Total number of S3 requests rejected for auth failure",
		Type:      counterMetric,
	}
}

func getS3RejectedHeaderRequestsTotalMD() MetricDescription {
	return MetricDescription{
		Namespace: s3MetricNamespace,
		Subsystem: requestsRejectedSubsystem,
		Name:      headerTotal,
		Help:      "Total number of S3 requests rejected for invalid header",
		Type:      counterMetric,
	}

	if s3Error != ErrNone && s3Error != ErrAccessDenied {
		writeErrorResponse(ctx, w, errorCodes.ToAPIErr(s3Error), r.URL)
		return
	}

	// Anonymous users, should be rejected.
	if cred.AccessKey == "" {
		writeErrorResponse(ctx, w, errorCodes.ToAPIErr(ErrAccessDenied), r.URL)
		return
	}

	// If etcd, dns federation configured list buckets from etcd.
	var bucketsInfo []BucketInfo