code: def _worker(self, clf):
          
          logger.debug(
              'worker %d is running, waiting for tasks from master at rank %d' %
              (MPI.COMM_WORLD.Get_rank(), self.master_rank)
          )
          comm = MPI.COMM_WORLD
          status = MPI.Status()
          while 1:
              task = comm.recv(source=self.master_rank,
                               tag=MPI.ANY_TAG,
                               status=status)
              if status.Get_tag():
                  break
              comm.send(self._voxel_scoring(task, clf),
                        dest=self.master_rank)
docs: Worker node's operation.
  
          Receiving tasks from the master to process and sending the result back
  
          Parameters
          ----------
          clf: classification function
              the classifier to be used in cross validation
  
          Returns
          -------
          None