code: def check_datafile_present_and_download(path, backup_url=None):
      
      path = Path(path)
      if path.is_file(): return True
      if backup_url is None: return False
      logg.info('try downloading from url\n' + backup_url + '\n' +
                '... this may take a while but only happens once')
      if not path.parent.is_dir():
          logg.info('creating directory', str(path.parent) + '/', 'for saving data')
          path.parent.mkdir(parents=True)
      from urllib.request import urlretrieve
      urlretrieve(backup_url, str(path), reporthook=download_progress)
      logg.info('')
      return True
docs: Check whether the file is present, otherwise download.