//// tab | Python 3.8+ alternative

```Python hl_lines="1  4"
{!> ../../docs_src/python_types/tutorial009b.py!}
```

////

#### Gebruik van `Union` of `Optional`

Als je een Python versie lager dan 3.10 gebruikt, is dit een tip vanuit mijn **subjectieve** standpunt:

* 🚨 Vermijd het gebruik van `Optional[EenType]`.
* Gebruik in plaats daarvan **`Union[EenType, None]`** ✨.

  }

  // enum singleton pattern
  private enum ToStringFunction implements Function<Object, String> {
    INSTANCE;

    @Override
    public String apply(Object o) {
      checkNotNull(o); // eager for GWT.
      return o.toString();
    }

    @Override
    public String toString() {
      return "Functions.toStringFunction()";
    }
  }

  /**
   * Returns the identity function.
   *

      return list.asList();
    }
    return copyFromCollection(elements);
  }

  @JsMethod
  public static <E> ImmutableList<E> copyOf(E[] elements) {
    checkNotNull(elements); // eager for GWT
    return copyOf(Arrays.asList(elements));
  }

  private static <E> ImmutableList<E> copyFromCollection(Collection<? extends E> collection) {
    Object[] elements = collection.toArray();

  }

  private static <K, V> ImmutableSetMultimap<K, V> copyOf(
      Multimap<? extends K, ? extends V> multimap,
      @Nullable Comparator<? super V> valueComparator) {
    checkNotNull(multimap); // eager for GWT
    if (multimap.isEmpty() && valueComparator == null) {
      return of();
    }

    if (multimap instanceof ImmutableSetMultimap) {

  }

  private static <K, V> ImmutableSetMultimap<K, V> copyOf(
      Multimap<? extends K, ? extends V> multimap,
      @Nullable Comparator<? super V> valueComparator) {
    checkNotNull(multimap); // eager for GWT
    if (multimap.isEmpty() && valueComparator == null) {
      return of();
    }

    if (multimap instanceof ImmutableSetMultimap) {

looking across the garden, called out `The Queen!  The Queen!'
and the three gardeners instantly threw themselves flat upon
their faces.  There was a sound of many footsteps, and Alice
looked round, eager to see the Queen.

  First came ten soldiers carrying clubs; these were all shaped
like the three gardeners, oblong and flat, with their hands and
feet at the corners:  next the ten courtiers; these were

    if (!expression) {
      throw new IllegalStateException(Platform.lenientFormat(errorMessageTemplate, p1, p2, p3, p4));
    }
  }

  /*
   * Preconditions.checkNotNull is *intended* for performing eager null checks on parameters that a
   * nullness checker can already "prove" are non-null. That means that the first parameter to
   * checkNotNull *should* be annotated to require it to be non-null.
   *

    size and duration. This feature is an unstable preview: the API is subject
    to change, and the implementation is incomplete. This is a big new API we
    are eager for feedback.

 *  New: Support ALPN via Google Play Services' Dynamic Security Provider. This
    expands HTTP/2 support to older Android devices that have Google Play
    Services.

LT",nextWeek:"dddd [kl.] LT",lastDay:"[i g\xe5r kl.] LT",lastWeek:"[forrige] dddd [kl.] LT",sameElse:"L"},relativeTime:{future:"om %s",past:"%s siden",s:"noen sekunder",ss:"%d sekunder",m:"ett minutt",mm:"%d minutter",h:"en time",hh:"%d timer",d:"en dag",dd:"%d dager",w:"en uke",ww:"%d uker",M:"en m\xe5ned",MM:"%d m\xe5neder",y:"ett \xe5r",yy:"%d \xe5r"},dayOfMonthOrdinalParse:/\d{1,2}\./,ordinal:"%d.",week:{dow:1,doy:4}});var er={1:"\u0967",2:"\u0968",3:"\u0969",4:"\u096a",5:"\u096b",6:"\u096c",7:"\u096d",8:"...

We expect this implementation to progress from alpha to beta and GA in coming releases, so we’re eager to have you comment about your dual-stack experiences in [#k8s-dual-stack](https://kubernetes.slack.com/messages/k8s-dual-stack) or in [enhancements #563](https://features.k8s.io/563). 

### go1.15.5