SQLModel que `id` es la **clave primaria** en la base de datos SQL (puedes aprender más sobre claves primarias de SQL en la documentación de SQLModel).

    Nota: Usamos `int | None` para el campo de clave primaria para que en el código Python podamos *crear un objeto sin un `id`* (`id=None`), asumiendo que la base de datos lo *generará al guardar*. SQLModel entiende que la base de datos proporcionará el `id` y *define la columna como un `INTEGER` no nulo* en el esquema de la base de datos. Consulta...

* `set`
* `dict`

Und Generics aus dem `typing`-Modul:

* `Union`
* `Optional`
* ... und andere.

////

### Klassen als Typen { #classes-as-types }

Sie können auch eine Klasse als Typ einer Variablen deklarieren.

Nehmen wir an, Sie haben eine Klasse `Person`, mit einem Namen:

{* ../../docs_src/python_types/tutorial010_py39.py hl[1:3] *}

Before Starlette `0.24.0`, a new instance of each middleware class would be created when a new middleware was added. That normally was not a problem, unless the middleware class expected to be created only once, with only one instance, that happened in some cases. This upgrade would solve those cases (thanks [@adriangb](https://github.com/adriangb)! Starlette PR [#2017](https://github.com/encode/starlette/pull/2017)). Now the middleware class instances are created once, right before the first request...

import okhttp3.internal.SuppressSignatureCheck

/** Data classes that correspond to each of the methods of [ConnectionListener]. */
@SuppressSignatureCheck
sealed class ConnectionEvent {
  abstract val timestampNs: Long
  open val connection: Connection?
    get() = null

  /** Returns if the event closes this event, or null if this is no open event. */
  open fun closes(event: ConnectionEvent): Boolean? = null

  val name: String

///

/// info | Información

También puedes usar:

* `response_model_exclude_defaults=True`
* `response_model_exclude_none=True`

        jvmThreadsObj.peak = threads.getPeakCount();
        final Classes classes = jvmStats.getClasses();
        final JvmClassesObj jvmClassesObj = new JvmClassesObj();
        jvmObj.classes = jvmClassesObj;
        jvmClassesObj.loaded = classes.getLoadedClassCount();
        jvmClassesObj.total_loaded = classes.getTotalLoadedClassCount();
        jvmClassesObj.unloaded = classes.getUnloadedClassCount();

     * </p>
     *
     * @param className the class name
     * @return <code>true</code> if the class file exists in the resources handled by this instance
     */
    boolean isExistClass(final String className);

    /**
     * Searches for classes handled by this instance and calls the handler for each class.
     * <p>
     * If a root package is specified at instance construction, only classes under the root package are targeted.
     * </p>

Die `Hero`-Klasse ist einem Pydantic-Modell sehr ähnlich (faktisch ist sie darunter tatsächlich *ein Pydantic-Modell*).

Es gibt ein paar Unterschiede:

* `table=True` sagt SQLModel, dass dies ein *Tabellenmodell* ist, es soll eine **Tabelle** in der SQL-Datenbank darstellen, es ist nicht nur ein *Datenmodell* (wie es jede andere reguläre Pydantic-Klasse wäre).

        List<Path> classes = dispatched.get(JavaPathType.CLASSES);
        List<Path> modules = dispatched.get(JavaPathType.MODULES);
        List<Path> unresolved = dispatched.get(PathType.UNRESOLVED);
        assertEquals(3, dispatched.size());
        assertEquals(1, unresolved.size());
        assertEquals(8, classes.size()); // "plexus.pom" and "junit.jar" are excluded.

    }

    @Test
    void testTargetPath() {
        Build build = mock(Build.class);
        when(build.getDirectory()).thenReturn("target");
        when(build.getOutputDirectory()).thenReturn("target/classes");
        when(build.getTestOutputDirectory()).thenReturn("target/test-classes");

        Project project = mock(Project.class);
        when(project.getBuild()).thenReturn(build);