docs: def _get_data(self, id_list, format='MLDataset'):
          """Returns the data, from all modalities, for a given list of IDs"""
  
          format = format.lower()
  
          features = list()  # returning a dict would be better if AutoMKL() can handle it
          for modality, data in self._modalities.items():
              if format in ('ndarray', 'data_matrix'):
                  # turning dict of arrays into a data matrix
                  # this is arguably worse, as labels are difficult to pass
                  subset = np.array(itemgetter(*id_list)(data))
              elif format in ('mldataset', 'pyradigm'):
                  # getting container with fake data
                  subset = self._dataset.get_subset(id_list)
                  # injecting actual features
                  subset.data = { id_: data[id_] for id_ in id_list }
              else:
                  raise ValueError('Invalid output format - choose only one of '
                                   'MLDataset or data_matrix')
  
              features.append(subset)
  
          return features