code: def _find_files(dl_paths, publisher, url_dict):
    
    if publisher == 'cnn':
      top_dir = os.path.join(dl_paths['cnn_stories'], 'cnn', 'stories')
    elif publisher == 'dm':
      top_dir = os.path.join(dl_paths['dm_stories'], 'dailymail', 'stories')
    else:
      logging.fatal('Unsupported publisher: %s', publisher)
    files = tf.io.gfile.listdir(top_dir)
  
    ret_files = []
    for p in files:
      basename = os.path.basename(p)
      if basename[0:basename.find('.story')] in url_dict:
        ret_files.append(os.path.join(top_dir, p))
    return ret_files
docs: Find files corresponding to urls.