def export_instance(self, instance, body, project_id=None):
        """
        
        """
        try:
            response = self.get_conn().instances().export(
                project=project_id,
                instance=instance,
                body=body
            ).execute(num_retries=self.num_retries)
            operation_name = response["name"]
            self._wait_for_operation_to_complete(project_id=project_id,
                                                 operation_name=operation_name)
        except HttpError as ex:
            raise AirflowException(
                'Exporting instance {} failed: {}'.format(instance, ex.content)
            )