```

////

The string will be checked to be a valid URL, and documented in JSON Schema / OpenAPI as such.

## Attributes with lists of submodels

You can also use Pydantic models as subtypes of `list`, `set`, etc.:

//// tab | Python 3.10+

```Python hl_lines="18"
{!> ../../docs_src/body_nested_models/tutorial006_py310.py!}
```

////

//// tab | Python 3.9+

    }
    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");

     * it.
     */
    setResult(transformResult);
  }

  /** Template method for subtypes to actually run the transform. */
  @ForOverride
  @ParametricNullness
  abstract T doTransform(F function, @ParametricNullness I result) throws Exception;

  /** Template method for subtypes to actually set the result. */
  @ForOverride
  abstract void setResult(@ParametricNullness T result);

  @Override

      return resultString + superString;
    }
    return null;
  }

  /** Template method for subtypes to actually run the fallback. */
  @ForOverride
  @ParametricNullness
  abstract T doFallback(F fallback, X throwable) throws Exception;

  /** Template method for subtypes to actually set the result. */
  @ForOverride
  abstract void setResult(@ParametricNullness T result);

  @Override

 * guarantees detailed below.
 *
 * <p><b>Warning:</b> avoid <i>direct</i> usage of {@link ImmutableCollection} as a type (just as
 * with {@link Collection} itself). Prefer subtypes such as {@link ImmutableSet} or {@link
 * ImmutableList}, which have well-defined {@link #equals} semantics, thus avoiding a common source
 * of bugs and confusion.
 *
 * <h3>About <i>all</i> {@code Immutable-} collections</h3>

   *       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