def substitute_models_with_pks(cls, model_dict: Dict) -> Dict:  # noqa  CCR001
        """
        Receives dictionary of model that is about to be saved and changes all related
        models that are stored as foreign keys to their fk value.

        :param model_dict: dictionary of model that is about to be saved
        :type model_dict: Dict
        :return: dictionary of model that is about to be saved
        :rtype: Dict
        """
        for field in cls.extract_related_names():
            field_value = model_dict.get(field, None)
            if field_value is not None:
                target_field = cls.ormar_config.model_fields[field]
                target_pkname = target_field.to.ormar_config.pkname
                if isinstance(field_value, ormar.Model):  # pragma: no cover
                    pk_value = getattr(field_value, target_pkname)
                    if not pk_value:
                        raise ModelPersistenceError(
                            f"You cannot save {field_value.get_name()} "
                            f"model without pk set!"
                        )
                    model_dict[field] = pk_value
                elif isinstance(field_value, (list, dict)) and field_value:
                    if isinstance(field_value, list):
                        model_dict[field] = [
                            target.get(target_pkname) for target in field_value
                        ]
                    else:
                        model_dict[field] = field_value.get(target_pkname)
                else:
                    model_dict.pop(field, None)
        return model_dict

        Receives dictionary of model that is about to be saved and changes all related
        models that are stored as foreign keys to their fk value.

        :param model_dict: dictionary of model that is about to be saved
        :type model_dict: Dict
        :return: dictionary of model that is about to be saved
        :rtype: Dict
        
ormar/models/mixins/save_mixin.py