code: def run(self, clf):
          
          rank = MPI.COMM_WORLD.Get_rank()
          if rank == self.master_rank:
              results = self._master()
              # Sort the voxels
              results.sort(key=lambda tup: tup[1], reverse=True)
          else:
              self._worker(clf)
              results = []
          return results
docs: Run correlation-based voxel selection in master-worker model.
  
          Sort the voxels based on the cross-validation accuracy
          of their correlation vectors
  
          Parameters
          ----------
          clf: classification function
              the classifier to be used in cross validation
  
          Returns
          -------
          results: list of tuple (voxel_id, accuracy)
              the accuracy numbers of all voxels, in accuracy descending order
              the length of array equals the number of voxels