prozorro_sale.jobber.models.mixins

        # TODO: remove this function when nested digitalSignature will be implemented
        self.ensure_owner_permission(context)
        if self.status != 'deleted':
            raise errors.ForbiddenStatusError(self._obj_type, self.status)
        if doc.documentType != 'digitalSignature':
            raise errors.DataError({'documentType': f'Cannot upload doc with documentType {doc.documentType}'})
        cancellation = self.cancellations[cancellation_id]
        cancellation.documents[doc.id] = doc
        return {'id': doc.id}