code: def extract_master_tarball(cls):
          
          if not os.path.exists(cls.master_tarball_file):
              cls.download_grids()
  
          with tarfile.open(os.path.join(ISOCHRONES, cls.master_tarball_file)) as tar:
              logging.info('Extracting {}...'.format(cls.master_tarball_file))
              tar.extractall(ISOCHRONES)
docs: Unpack tarball of tarballs