pass

    model = ModelWithCustomEncoder(dt_field=datetime(2019, 1, 1, 8))
    assert jsonable_encoder(model) == {"dt_field": "2019-01-01T08:00:00+00:00"}
    subclass_model = ModelWithCustomEncoderSubclass(dt_field=datetime(2019, 1, 1, 8))
    assert jsonable_encoder(subclass_model) == {"dt_field": "2019-01-01T08:00:00+00:00"}


# TODO: remove when deprecating Pydantic v1
@needs_pydanticv1

* Decompressing gzip-compressed request bodies.
* Automatically logging all request bodies.

## Handling custom request body encodings

Let's see how to make use of a custom `Request` subclass to decompress gzip requests.

And an `APIRoute` subclass to use that custom request class.

### Create a custom `GzipRequest` class

!!! tip

This simple case is handled automatically by FastAPI because the return type annotation is the class (or a subclass) of `Response`.

And tools will also be happy because both `RedirectResponse` and `JSONResponse` are subclasses of `Response`, so the type annotation is correct.

### Annotate a Response Subclass

You can also use a subclass of `Response` in the type annotation:

```Python hl_lines="8-9"

    private static ClassOwnership detectJvmBehavior() {
      class LocalClass<T> {}
      Class<?> subclass = new LocalClass<String>() {}.getClass();
      // requireNonNull is safe because we're examining a type that's known to have a superclass.
      ParameterizedType parameterizedType =
          requireNonNull((ParameterizedType) subclass.getGenericSuperclass());
      for (ClassOwnership behavior : ClassOwnership.values()) {

        }

        return request;
    }

    // layer the creation of a project builder configuration with a request, but this will need to be
    // a Maven subclass because we don't want to couple maven to the project builder which we need to
    // separate.
    protected MavenSession createMavenSession(File pom) throws Exception {
        return createMavenSession(pom, new Properties());

        }

        return request;
    }

    // layer the creation of a project builder configuration with a request, but this will need to be
    // a Maven subclass because we don't want to couple maven to the project builder which we need to
    // separate.
    protected MavenSession createMavenSession(File pom) throws Exception {
        return createMavenSession(pom, new Properties());

   * This is useful if the function instance already exists, or so that you can supply a lambda
   * expressions. If those circumstances don't apply, you probably don't need to use this; subclass
   * {@code TreeTraverser} and implement its {@link #children} method directly.
   *
   * @since 20.0
   * @deprecated Use {@link com.google.common.graph.Traverser#forTree} instead. If you are using a

 * <i>chaining</i>, and <i>using</i>.
 *
 * <h4>Acquiring</h4>
 *
 * <p>The common ways to get an instance of {@code Ordering} are:
 *
 * <ul>
 *   <li>Subclass it and implement {@link #compare} instead of implementing {@link Comparator}
 *       directly
 *   <li>Pass a <i>pre-existing</i> {@link Comparator} instance to {@link #from(Comparator)}

   *
   * @since 2.0
   */
  public static class Builder<E> extends ImmutableCollection.Builder<E> {
    /*
     * `contents` is null only for instances of the subclass, ImmutableSortedMultiset.Builder. That
     * subclass overrides all the methods that access it here. Thus, all the methods here can safely
     * assume that this field is non-null.
     */
    @CheckForNull ObjectCountHashMap<E> contents;

   * elements and to build again.
   *
   * @since 2.0
   */
  public static class Builder<E> extends ImmutableCollection.Builder<E> {
    /*
     * `impl` is null only for instances of the subclass, ImmutableSortedSet.Builder. That subclass
     * overrides all the methods that access it here. Thus, all the methods here can safely assume
     * that this field is non-null.
     */
    @CheckForNull private SetBuilderImpl<E> impl;