use_case.py

class CreateJob(UseCaseInterface):
    def __init__(
        self,
        repository: JobRepositoryInterface,
        title,
        date_start,
        date_end,
        slug=None
    ):
        self._title = title
        self._date_start = date_start
        self._date_end = date_end
        self._slug = None
        # -- Other objects
        self.__obj = None # To use with is valid
        self._repository = repository

     @property
     def repository(self) -> JobRepositoryInterface:
         return self._repository

    def execute(self) -> Job:
        self._factory()
        self.is_valid()
        self.__obj.slug = self._generate_slug(job.id, job.title)
        self._repository.save(self.__obj) # This calls self.__obj.save()
        return self.__obj

    def is_valid(self):
        # Check date order
        if self._date_end and self._date_start and self._date_end <= self._date_start:
            # raise ValidationError(_("Start date should be before end date"))
            raise InvalidDateOrder(_("Start date should be before end date"))

        # Executa programatically model validations. Raises validation error.
        if not self.__obj:
            self._factory()
        self.__obj.full_clean()
        return True

    def _generate_slug(self, uuid, title):
        return slug_generator(uuid, title)

    def _factory(self):
        """Create an instance of a Job, and save it into self.__obj"""
        # Remove _ from keys, so we pass correct arguments to create,
        # and leave values that are not None
        params = {k[1:] if k[0] == '_' else k:v for k,v in self.__dict__.items() if v is not None}
        self.__obj = self._repository.factory(**params)