class_docstr: Activity-based voxel selection component of FCMA
  
  Parameters
  ----------
  
  data: 4D array in shape [brain 3D + epoch]
      contains the averaged and normalized brain data epoch by epoch.
      It is generated by .io.prepare_searchlight_mvpa_data
  
  mask: 3D array
  
  labels: 1D array
      contains the labels of the epochs.
      It is generated by .io.prepare_searchlight_mvpa_data
  
  num_folds: int
      the number of folds to be conducted in the cross validation
  
  sl: Searchlight
      the distributed Searchlight object
code: def __init__(self, data, mask, labels, num_folds, sl):
      self.data = data
      self.mask = mask.astype(np.bool)
      self.labels = labels
      self.num_folds = num_folds
      self.sl = sl
      num_voxels = np.sum(self.mask)
      if num_voxels == 0:
          raise ValueError("Zero processed voxels")
  
file_path: brainiak/brainiak/fcma/mvpa_voxelselector.py
imports: import numpy
  from sklearn import model_selection
  import logging
  from mpi4py import MPI
label_desc: Use image node_id 1 to create a new MVPAVoxelSelector object  with example: obj = MVPAVoxelSelector(data, mask, labels, num_folds, sl)