* @throws NullPointerException if any element in the stream is {@code null}.
   * @return {@code Optional.of(onlyElement)} if the stream has exactly one element (must not be
   *     {@code null}) and returns {@code Optional.empty()} if it has none.
   */
  @SuppressWarnings("unchecked")
  public static <T> Collector<T, ?, Optional<T>> toOptional() {
    return (Collector) TO_OPTIONAL;
  }

            @Nonnull
            @Override
            public Optional<Source> getInstallationToolchainsSource() {
                return Optional.ofNullable(installationToolchainsSource);
            }

            @Nonnull
            @Override
            public Optional<Source> getUserToolchainsSource() {
                return Optional.ofNullable(userToolchainsSource);
            }
        }
    }

  // the smallest value of such global default PriorityClasses will be used as the default priority.
  // +optional
  optional bool globalDefault = 3;

  // description is an arbitrary string that usually provides guidelines on
  // when this priority class should be used.
  // +optional
  optional string description = 4;

  // preemptionPolicy is the Policy for preempting pods with lower priority.

  // +optional
  optional k8s.io.apimachinery.pkg.apis.meta.v1.ObjectMeta metadata = 1;

  // spec represents specification of the RuntimeClass
  // More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#spec-and-status
  optional RuntimeClassSpec spec = 2;
}

// RuntimeClassList is a list of RuntimeClass objects.

```

////

#### `Union` oder `Optional` verwenden?

Wenn Sie eine Python-Version unterhalb 3.10 verwenden, hier ist mein sehr **subjektiver** Standpunkt dazu:

* 🚨 Vermeiden Sie `Optional[SomeType]`
* Stattdessen ✨ **verwenden Sie `Union[SomeType, None]`** ✨.

        return versionRange.isSelectedVersionKnown(this);
    }

    @Override
    public void setOptional(boolean optional) {
        this.optional = optional;
    }

  // the smallest value of such global default PriorityClasses will be used as the default priority.
  // +optional
  optional bool globalDefault = 3;

  // description is an arbitrary string that usually provides guidelines on
  // when this priority class should be used.
  // +optional
  optional string description = 4;

  // preemptionPolicy is the Policy for preempting pods with lower priority.

        }
    }

    @Override
    public Optional<Boolean> force() {
        if (commandLine.hasOption(CLIManager.FORCE)) {
            return Optional.of(Boolean.TRUE);
        }
        return Optional.empty();
    }

    @Override
    public Optional<Boolean> yes() {
        if (commandLine.hasOption(CLIManager.YES)) {
            return Optional.of(Boolean.TRUE);
        }
        return Optional.empty();

  // Standard object's metadata.
  // More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#metadata
  // +optional
  optional k8s.io.apimachinery.pkg.apis.meta.v1.ObjectMeta metadata = 1;

  // Status is filled in by the server with the user attributes.
  optional SelfSubjectReviewStatus status = 2;
}

// SelfSubjectReviewStatus is filled by the kube-apiserver and sent back to a user.

			Description: `set Content-Security-Policy response header value` + defaultHelpPostfix(browserCSPPolicy),
			Optional:    true,
			Type:        "string",
		},
		config.HelpKV{
			Key:         browserHSTSSeconds,
			Description: `set Strict-Transport-Security 'max-age' amount of seconds value` + defaultHelpPostfix(browserHSTSSeconds),
			Optional:    true,
			Type:        "number",
		},
		config.HelpKV{