def start_instance(self, zone, resource_id, project_id=None):
        """
        
        """
        response = self.get_conn().instances().start(
            project=project_id,
            zone=zone,
            instance=resource_id
        ).execute(num_retries=self.num_retries)
        try:
            operation_name = response["name"]
        except KeyError:
            raise AirflowException(
                "Wrong response '{}' returned - it should contain "
                "'name' field".format(response))
        self._wait_for_operation_to_complete(project_id=project_id,
                                             operation_name=operation_name,
                                             zone=zone)