# as is just because it's an instance of a subclass of a more limited class
            # e.g. UserInDB (containing hashed_password) could be a subclass of User
            # that doesn't have the hashed_password. But because it's a subclass, it
            # would pass the validation and be returned as is.

 * a lot of busy work, and the annotation matters only when the APIs to be annotated are visible to
 * Kotlin code. In this class, nothing is publicly visible (nor exposed indirectly through a
 * publicly visible subclass), and I doubt any of our current or future Kotlin extensions for the
 * package will refer to the class. Plus, @ParametricNullness is only a temporary workaround,

 * a lot of busy work, and the annotation matters only when the APIs to be annotated are visible to
 * Kotlin code. In this class, nothing is publicly visible (nor exposed indirectly through a
 * publicly visible subclass), and I doubt any of our current or future Kotlin extensions for the
 * package will refer to the class. Plus, @ParametricNullness is only a temporary workaround,

  public <T> void testRejectTypeVariable_withOwnerType() {
    // Neither has subclass
    assertHasTypeVariable(new From<Integer>().new To<String>().type());
    assertHasTypeVariable(new From<T>().new To<String>().type());
    assertHasTypeVariable(new From<Integer>().new To<T>().type());

    // Owner is subclassed
    assertHasTypeVariable(new From<Integer>() {}.new To<String>().type());

   */
  public static <K extends @Nullable Object, V extends @Nullable Object> SortedMap<K, V> filterKeys(
      SortedMap<K, V> unfiltered, final Predicate<? super K> keyPredicate) {
    // TODO(lowasser): Return a subclass of Maps.FilteredKeyMap for slightly better
    // performance.
    return filterEntries(unfiltered, Maps.<K>keyPredicateOnEntries(keyPredicate));
  }

  /**

   */
  public static <K extends @Nullable Object, V extends @Nullable Object> SortedMap<K, V> filterKeys(
      SortedMap<K, V> unfiltered, final Predicate<? super K> keyPredicate) {
    // TODO(lowasser): Return a subclass of Maps.FilteredKeyMap for slightly better
    // performance.
    return filterEntries(unfiltered, Maps.<K>keyPredicateOnEntries(keyPredicate));
  }

  /**

  public <T> void testRejectTypeVariable_withOwnerType() {
    // Neither has subclass
    assertHasTypeVariable(new From<Integer>().new To<String>().type());
    assertHasTypeVariable(new From<T>().new To<String>().type());
    assertHasTypeVariable(new From<Integer>().new To<T>().type());

    // Owner is subclassed
    assertHasTypeVariable(new From<Integer>() {}.new To<String>().type());

    return (Segment<K, V, E, S>[]) new Segment<?, ?, ?, ?>[ssize];
  }

  // Inner Classes

  /**
   * Segments are specialized versions of hash tables. This subclass inherits from ReentrantLock
   * opportunistically, just to simplify some locking and avoid separate construction.
   */
  @SuppressWarnings("serial") // This class is never serialized.
  abstract static class Segment<

    return (Segment<K, V, E, S>[]) new Segment<?, ?, ?, ?>[ssize];
  }

  // Inner Classes

  /**
   * Segments are specialized versions of hash tables. This subclass inherits from ReentrantLock
   * opportunistically, just to simplify some locking and avoid separate construction.
   */
  @SuppressWarnings("serial") // This class is never serialized.
  abstract static class Segment<

Na realidade, `Query`, `Path` e outros que você verá em seguida, criam objetos de subclasses de uma classe `Param` comum, que é ela mesma uma subclasse da classe `FieldInfo` do Pydantic.

E `Field` do Pydantic retorna uma instância de `FieldInfo` também.

`Body` também retorna objetos de uma subclasse de `FieldInfo` diretamente. E tem outras que você verá mais tarde que são subclasses da classe `Body`.