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

## Attributes with lists of submodels { #attributes-with-lists-of-submodels }

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

{* ../../docs_src/body_nested_models/tutorial006_py310.py hl[18] *}

This will expect (convert, validate, document, etc.) a JSON body like:

```JSON hl_lines="11"
{

 * detailed at {@link ImmutableCollection}.
 *
 * <p><b>Warning:</b> avoid <i>direct</i> usage of {@link ImmutableMultimap} as a type (as with
 * {@link Multimap} itself). Prefer subtypes such as {@link ImmutableSetMultimap} or {@link
 * ImmutableListMultimap}, which have well-defined {@link #equals} semantics, thus avoiding a common
 * source of bugs and confusion.
 *

 * detailed at {@link ImmutableCollection}.
 *
 * <p><b>Warning:</b> avoid <i>direct</i> usage of {@link ImmutableMultimap} as a type (as with
 * {@link Multimap} itself). Prefer subtypes such as {@link ImmutableSetMultimap} or {@link
 * ImmutableListMultimap}, which have well-defined {@link #equals} semantics, thus avoiding a common
 * source of bugs and confusion.
 *

                            message["content-type"] = content_type_value
                            if message.get_content_maintype() == "application":
                                subtype = message.get_content_subtype()
                                if subtype == "json" or subtype.endswith("+json"):
                                    json_body = await request.json()
                        if json_body != Undefined:

* Add 4 Japanese articles to [External Links](https://fastapi.tiangolo.com/external-links/). PR [#783](https://github.com/tiangolo/fastapi/pull/783) by [@HymanZHAN](https://github.com/HymanZHAN).
* Add support for subtypes of main types in `jsonable_encoder`, e.g. asyncpg's UUIDs. PR [#756](https://github.com/tiangolo/fastapi/pull/756) by [@RmStorm](https://github.com/RmStorm).