[FastAPI docs for JSON Compatible Encoder](https://fastapi.tiangolo.com/tutorial/encoder/).
    """
    custom_encoder = custom_encoder or {}
    if custom_encoder:
        if type(obj) in custom_encoder:
            return custom_encoder[type(obj)](obj)
        else:
            for encoder_type, encoder_instance in custom_encoder.items():
                if isinstance(obj, encoder_type):
                    return encoder_instance(obj)

        pass

    class MyModel(BaseModel):
        dt_field: safe_datetime

    instance = MyModel(dt_field=safe_datetime.now())

    encoded_instance = jsonable_encoder(
        instance, custom_encoder={safe_datetime: lambda o: o.isoformat()}
    )
    assert encoded_instance["dt_field"] == instance.dt_field.isoformat()


def test_custom_enum_encoders():
    def custom_enum_encoder(v: Enum):

* Fix typos in docs. PR [734](https://github.com/tiangolo/fastapi/pull/734) by [@bundabrg](https://github.com/bundabrg).
* Fix usage of `custom_encoder` in `jsonable_encoder`. PR [#715](https://github.com/tiangolo/fastapi/pull/715) by [@matrixise](https://github.com/matrixise).