{*../../docs_src/python_types/tutorial009.py hl[1,4] *}

Utiliser `Optional[str]` plutôt que `str` permettra à l'éditeur de vous aider à détecter les erreurs où vous supposeriez qu'une valeur est toujours de type `str`, alors qu'elle pourrait aussi être `None`.

#### Types génériques

Les types qui peuvent contenir des paramètres de types entre crochets, comme :

    boolean isMatchingProject(MavenProject project, String selector, File reactorDirectory) {
        // [groupId]:artifactId
        if (selector.contains(":")) {
            String id = ':' + project.getArtifactId();

            if (id.equals(selector)) {
                return true;
            }

            id = project.getGroupId() + id;

            return id.equals(selector);
        }

	envoy.PersistentFlags().StringVarP(&labelSelector, "selector", "l", "", "Label selector")
	envoy.PersistentFlags().IntVar(&proxyAdminPort, "ui-port", util.DefaultProxyAdminPort, "The component dashboard UI port.")
	dashboardCmd.AddCommand(envoy)

	proxy := proxyDashCmd(cliContext)
	proxy.PersistentFlags().StringVarP(&labelSelector, "selector", "l", "", "Label selector")

                        }
                    }
                    boolean optional = false;
                    if (!selector.isEmpty() && selector.charAt(0) == '?') {
                        optional = true;
                        selector = selector.substring(1);
                    }
                    projectActivation.addProjectActivation(selector, active, optional);

* Validación de datos
* Documentación automática

## Configuraciones por defecto

Como los parámetros de query no están fijos en una parte del path pueden ser opcionales y pueden tener valores por defecto.

El ejemplo arriba tiene `skip=0` y `limit=10` como los valores por defecto.

Entonces, si vas a la URL:

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

Sería lo mismo que ir a:

	}
	pod, _, err := getFirstPodFunc(client, namespace, selector, timeout, sortBy)
	if err != nil {
		return "", "", fmt.Errorf("no pods match %q", resname)
	}
	return pod.Name, namespace, nil
}

// SelectorsForObject is a fork of upstream function to add additional Istio type support
func SelectorsForObject(object runtime.Object) (namespace string, selector labels.Selector, err error) {
	switch t := object.(type) {

(document.getElementById(prefix))\n    return prefix\n  },\n\n  getSelectorFromElement(element) {\n    let selector = element.getAttribute('data-target')\n\n    if (!selector || selector === '#') {\n      const hrefAttr = element.getAttribute('href')\n      selector = hrefAttr && hrefAttr !== '#' ? hrefAttr.trim() : ''\n    }\n\n    try {\n      return document.querySelector(selector) ? selector : null\n    } catch (err) {\n      return null\n    }\n  },\n\n  getTransitionDurationFromElement(element)...

                        }
                    }
                    boolean optional = false;
                    if (!selector.isEmpty() && selector.charAt(0) == '?') {
                        optional = true;
                        selector = selector.substring(1);
                    }
                    projectActivation.addProjectActivation(selector, active, optional);
                }

//
// This is intended to be used when a peer failure is detected.
TF_CAPI_EXPORT extern void TFE_AbortCollectiveOps(TFE_Context* ctx,
                                                  TF_Status* status);

// Checks the health of collective ops peers. Explicit health check is needed in
// multi worker collective ops to detect failures in the cluster.  If a peer is
// down, collective ops may hang.

		nsMatchedLabels := make([]string, 0)
		podMatchedLabels := make([]string, 0)
		extractMatchLabels := func(selector *metav1.LabelSelector) []string {
			if selector == nil {
				return nil
			}
			labels := make([]string, 0)
			for _, me := range selector.MatchExpressions {
				if me.Operator != metav1.LabelSelectorOpIn {
					continue
				}
				for _, v := range me.Values {