}
    ParameterizedType subtype =
        (ParameterizedType)
            new TypeToken<BaseWithTypeVar<List<?>>>() {}.getSubtype(Outer.Sub.class).getType();
    assertEquals(Outer.Sub.class, subtype.getRawType());
    assertThat(subtype.getActualTypeArguments()[0]).isInstanceOf(WildcardType.class);
    ParameterizedType owner = (ParameterizedType) subtype.getOwnerType();

    return create(AUDIO_TYPE, subtype);
  }

  /**
   * Creates a media type with the "font" type and the given subtype.
   *
   * @throws IllegalArgumentException if subtype is invalid
   */
  static MediaType createFontType(String subtype) {
    return create(FONT_TYPE, subtype);
  }

  /**
   * Creates a media type with the "image" type and the given subtype.
   *

    }
    ParameterizedType subtype =
        (ParameterizedType)
            new TypeToken<BaseWithTypeVar<List<?>>>() {}.getSubtype(Outer.Sub.class).getType();
    assertEquals(Outer.Sub.class, subtype.getRawType());
    assertThat(subtype.getActualTypeArguments()[0]).isInstanceOf(WildcardType.class);
    ParameterizedType owner = (ParameterizedType) subtype.getOwnerType();

    assertEquals("application", newType.type());
    assertEquals("yams", newType.subtype());
  }

  public void testCreateAudioType() {
    MediaType newType = MediaType.createAudioType("yams");
    assertEquals("audio", newType.type());
    assertEquals("yams", newType.subtype());
  }

  public void testCreateFontType() {
    MediaType newType = MediaType.createFontType("yams");

   *       Serializable}.
   *   <li>Serialization test is not performed on method return values unless the method is a
   *       visible static factory method whose return type is {@code C} or {@code C}'s subtype.
   * </ul>
   *
   * <p>In all cases, if {@code C} needs custom logic for testing serialization, you can add an
   * explicit {@code testSerializable()} test in the corresponding {@code CTest} class, and {@code

   *       Serializable}.
   *   <li>Serialization test is not performed on method return values unless the method is a
   *       visible static factory method whose return type is {@code C} or {@code C}'s subtype.
   * </ul>
   *
   * <p>In all cases, if {@code C} needs custom logic for testing serialization, you can add an
   * explicit {@code testSerializable()} test in the corresponding {@code CTest} class, and {@code

func (input *InputSerialization) IsEmpty() bool {
	return !input.unmarshaled
}

// UnmarshalXML - decodes XML data.
func (input *InputSerialization) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
	// Make subtype to avoid recursive UnmarshalXML().
	type subInputSerialization InputSerialization
	parsedInput := subInputSerialization{}
	if err := d.DecodeElement(&parsedInput, &start); err != nil {
		return errMalformedXML(err)
	}

 *   <li>graphs that do/don't allow self-loops
 *   <li>graphs whose nodes/edges are insertion-ordered, sorted, or unordered
 *   <li>graphs whose edges have associated values
 * </ul>
 *
 * <p>{@code ValueGraph}, as a subtype of {@code Graph}, explicitly does not support parallel edges,
 * and forbids implementations or extensions with parallel edges. If you need parallel edges, use

   * @throws NullPointerException if any of {@code elements} is null
   */
  public static <E> ImmutableSortedSet<E> copyOf(Iterable<? extends E> elements) {
    // Hack around E not being a subtype of Comparable.
    // Unsafe, see ImmutableSortedSetFauxverideShim.
    @SuppressWarnings("unchecked")
    Ordering<E> naturalOrder = (Ordering<E>) Ordering.<Comparable<?>>natural();
    return copyOf(naturalOrder, elements);

# Body - Nested Models

With **FastAPI**, you can define, validate, document, and use arbitrarily deeply nested models (thanks to Pydantic).

## List fields

You can define an attribute to be a subtype. For example, a Python `list`:

//// tab | Python 3.10+

```Python hl_lines="12"
{!> ../../docs_src/body_nested_models/tutorial001_py310.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="14"