Pydantic heeft een speciaal gedrag wanneer je `Optional` of `Union[EenType, None]` gebruikt zonder een standaardwaarde, je kunt er meer over lezen in de Pydantic-documentatie over <a href="https://docs.pydantic.dev/2.3/usage/models/#required-fields" class="external-link" target="_blank">Verplichte optionele velden</a>.

///

## Type Hints met Metadata Annotaties

**Spoiler alert**: the tutorial - user guide includes:

* Declaration of **parameters** from other different places as: **headers**, **cookies**, **form fields** and **files**.
* How to set **validation constraints** as `maximum_length` or `regex`.

    val point = Point(null, 9L)
    assertThat(Point.ADAPTER.fromDer(bytes)).isEqualTo(point)
    assertThat(Point.ADAPTER.toDer(point)).isEqualTo(bytes)
  }

  @Test fun `point with both fields set`() {
    val bytes = "3006800109810109".decodeHex()
    val point = Point(9L, 9L)
    assertThat(Point.ADAPTER.fromDer(bytes)).isEqualTo(point)
    assertThat(Point.ADAPTER.toDer(point)).isEqualTo(bytes)
  }

  /**
   * Divides an iterator into unmodifiable sublists of the given size (the final list may be
   * smaller). For example, partitioning an iterator containing {@code [a, b, c, d, e]} with a
   * partition size of 3 yields {@code [[a, b, c], [d, e]]} -- an outer iterator containing two
   * inner lists of three and two elements, all in the original order.
   *
   * <p>The returned lists implement {@link java.util.RandomAccess}.
   *

        // Test crawlerList
        final List<Crawler> crawlerList = new ArrayList<>();
        indexUpdater.setCrawlerList(crawlerList);
        // Verify crawlerList was set (cannot access private field directly)

        // Test executeTime
        assertEquals(0L, indexUpdater.getExecuteTime());

        // Test documentSize
        assertEquals(0L, indexUpdater.getDocumentSize());
    }

**Peringatan spoiler**: tutorial - panduan pengguna termasuk:

* Deklarasi **parameter** dari tempat berbeda seperti: **header**, **cookie**, **form field** and **file**.
* Bagaimana mengatur **batasan validasi** seperti `maximum_length`atau `regex`.

  private final ReentrantLock lock;

  /**
   * The guards associated with this monitor that currently have waiters ({@code waiterCount > 0}).
   * A linked list threaded through the Guard.next field.
   */
  @GuardedBy("lock")
  private @Nullable Guard activeGuards = null;

  /**
   * Creates a monitor with a non-fair (but fast) ordering policy. Equivalent to {@code
   * Monitor(false)}.
   */

**Spoiler alert**: the tutorial - user guide includes:

* Declaration of **parameters** from other different places as: **headers**, **cookies**, **form fields** and **files**.
* How to set **validation constraints** as `maximum_length` or `regex`.

  }

  final transient ImmutableMap<K, ? extends ImmutableCollection<V>> map;
  final transient int size;

  // These constants allow the deserialization code to set final fields. This
  // holder class makes sure they are not initialized unless an instance is
  // deserialized.
  @GwtIncompatible
  @J2ktIncompatible
  static final class FieldSettersHolder {

    return getInet4Address(Arrays.copyOfRange(ip.getAddress(), 2, 6));
  }

  /**
   * A simple immutable data class to encapsulate the information to be found in a Teredo address.
   *
   * <p>All of the fields in this class are encoded in various portions of the IPv6 address as part
   * of the protocol. More protocols details can be found at: <a target="_parent"
   * href="http://en.wikipedia.org/wiki/Teredo_tunneling">http://en.wikipedia.