docs: def write_data(self, data, data_file, compression=0):
      """Writes the given *preprocessed* data to a file with the given name.
      """
      f = bob.io.base.HDF5File(data_file, 'w')
      f.set("rate", data[0], compression=compression)
      f.set("data", data[1], compression=compression)
      f.set("labels", data[2], compression=compression)