Launch next task or finish operation

        :param kser.sequencing.task.Task task: previous task
        :param cdumay_result.Result result: previous task result

        :return: Execution result
        :rtype: cdumay_result.Result

def launch_next(self, task=None, result=None):
        """ Launch next task or finish operation

        :param kser.sequencing.task.Task task: previous task
        :param cdumay_result.Result result: previous task result

        :return: Execution result
        :rtype: cdumay_result.Result
        """
        if task:
            next_task = self.next(task)
            if next_task:
                return next_task.send(result=result)
            else:
                return self.set_status(task.status, result)
        elif len(self.tasks) > 0:
            return self.tasks[0].send(result=result)
        else:
            return Result(retcode=1, stderr="Nothing to do, empty operation !")