docs: def _save(self, hdf5, model, positives, negatives):
      """Saves the given intermediate state of the bootstrapping to file."""
      # write the model and the training set indices to the given HDF5 file
      hdf5.set("PositiveIndices", sorted(list(positives)))
      hdf5.set("NegativeIndices", sorted(list(negatives)))
      hdf5.create_group("Model")
      hdf5.cd("Model")
      model.save(hdf5)
      del hdf5