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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def delete_relationship(self, session, data, api_type, obj_id, rel_key):
 """ Delete a resource or multiple resources from a to-many relationship. :param session: SQLAlchemy session :param data: JSON data provided with the request :param api_type: Type of the resource :param obj_id: ID of the resource :param rel_key: Key of the relationship to fetch """

        model = self._fetch_model(api_type)
        resource = self._fetch_resource(session, api_type, obj_id,
                                        Permissions.EDIT)
        relationship = self._get_relationship(resource, rel_key,
                                              Permissions.DELETE)
        self._check_json_data(data)

        if not isinstance(data['data'], list):
            raise ValidationError('Provided data must be an array.')

        if relationship.direction == MANYTOONE:
            return ToManyExpectedError(model, resource, relationship)

        response = JSONAPIResponse()
        response.data = {'data': []}

        session.add(resource)

        remove = get_rel_desc(resource, relationship.key,
                              RelationshipActions.DELETE)
        reverse_side = relationship.back_populates

        for item in data['data']:
            item = self._fetch_resource(session, item['type'], item['id'],
                                        Permissions.EDIT)

            if reverse_side:
                reverse_rel = item.__mapper__.relationships[reverse_side]

                if reverse_rel.direction == MANYTOONE:
                    permission = Permissions.EDIT
                else:
                    permission = Permissions.DELETE

                check_permission(item, reverse_side, permission)

            remove(resource, item)

        session.commit()
        session.refresh(resource)

        get = get_rel_desc(resource, relationship.key, RelationshipActions.GET)

        for item in get(resource):
            response.data['data'].append(self._render_short_instance(item))

        return response