{*../../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 :

* `List`

Isso inclui muitas bibliotecas que interagem com armazenamento em nuvem, processamento de vídeos, entre outras.

```{ .python .annotate hl_lines="2  10-12  14" }
{!../../docs_src/custom_response/tutorial008.py!}
```

1. Essa é a função geradora. É definida como "função geradora" porque contém declarações `yield` nela.

  }

  @Override
  protected void expectMissing(Entry<K, V>... entries) {
    for (Entry<K, V> entry : entries) {
      assertFalse("Should not contain entry " + entry, actualContents().contains(entry));
      assertFalse(
          "Should not contain key " + entry.getKey() + " mapped to value " + entry.getValue(),
          equal(getMap().get(entry.getKey()), entry.getValue()));
    }
  }

          reverse(samples.e4()));
    }

    private Entry<V, K> reverse(Entry<K, V> entry) {
      checkNotNull(entry);
      return mapEntry(entry.getValue(), entry.getKey());
    }

    @SuppressWarnings("unchecked")
    @Override
    public BiMap<V, K> create(Object... elements) {
      Entry<?, ?>[] entries = new Entry<?, ?>[elements.length];
      for (int i = 0; i < elements.length; i++) {

  static <K extends @Nullable Object, V extends @Nullable Object> Entry<V, K> reverseEntry(
      Entry<K, V> entry) {
    return mapEntry(entry.getValue(), entry.getKey());
  }

  @Override
  protected void expectContents(Collection<Entry<K, V>> expected) {
    super.expectContents(expected);
    List<Entry<V, K>> reversedEntries = new ArrayList<>();
    for (Entry<K, V> entry : expected) {
      reversedEntries.add(reverseEntry(entry));

    /**
     * construct a single vertex
     */
    public MetadataGraph(MetadataGraphVertex entry) throws MetadataResolutionException {
        checkVertex(entry);
        checkVertices(1);

        entry.setCompareVersion(versionedVertices);
        entry.setCompareScope(scopedVertices);

        vertices.add(entry);
        this.entry = entry;
    }
    // ------------------------------------------------------------------------

  }

  @MapFeature.Require(SUPPORTS_PUT)
  @CollectionSize.Require(absent = ZERO)
  public void testPutDuplicateValue() {
    List<Entry<K, V>> entries = copyToList(multimap().entries());

    for (Entry<K, V> entry : entries) {
      resetContainer();

      K k = entry.getKey();
      V v = entry.getValue();

      List<V> values = multimap().get(k);
      List<V> expectedValues = copyToList(values);

            // requireNonNull is safe because the first `size` elements have been filled in.
            Entry<K, V> prevEntry = requireNonNull(entryArray[i - 1]);
            Entry<K, V> entry = requireNonNull(entryArray[i]);
            K key = entry.getKey();
            V value = entry.getValue();
            checkEntryNotNull(key, value);
            keys[i] = key;
            values[i] = value;

      Collection<Entry<K, V>> originalEntries = mapGenerator.getSampleElements(elements.length);

      // Create a copy of that, with the desired value for each key
      Collection<Entry<K, V>> entries = new ArrayList<>(elements.length);
      int i = 0;
      for (Entry<K, V> entry : originalEntries) {
        entries.add(mapEntry(keysArray[i++], entry.getValue()));
      }

  }

  boolean removeEntriesIf(Predicate<? super Entry<K, Collection<V>>> predicate) {
    Iterator<Entry<K, Collection<V>>> entryIterator = unfiltered.asMap().entrySet().iterator();
    boolean changed = false;
    while (entryIterator.hasNext()) {
      Entry<K, Collection<V>> entry = entryIterator.next();
      K key = entry.getKey();
      Collection<V> collection = filterCollection(entry.getValue(), new ValuePredicate(key));