docs: def load_features_and_arrays(prefix, mmap_mode='r'):
      """
      Returns the features and NumPy arrays that were saved with
      save_features_and_arrays.
  
      Parameters
      ----------
  
      prefix : str
          Path to where data are saved
  
      mmap_mode : {None, 'r+', 'r', 'w+', 'c'}
          Mode in which to memory-map the file.  See np.load for details.
      """
      features = pybedtools.BedTool(prefix + '.features')
      arrays = np.load(prefix + '.npz', mmap_mode=mmap_mode)
      return features, arrays