docs: 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 !")