* Fix encoding of Pydantic models that inherit from others models with custom `json_encoders`. PR [#1769](https://github.com/tiangolo/fastapi/pull/1769) by [@henrybetts](https://github.com/henrybetts).
* Simplify and improve `jsonable_encoder`. PR [#1754](https://github.com/tiangolo/fastapi/pull/1754) by [@MashhadiNima](https://github.com/MashhadiNima).
* Simplify internal code syntax in several points. PR [#1753](https://github.com/tiangolo/fastapi/pull/1753) by [@uriyyo](https://github.com/uriyyo).