code: def start(self):
          
          self.logger.info('开始')
          videofiles = self._filter_path(self.path)
          l = len(videofiles)
          if l == 0:
              self.logger.info(
                  '在 {} 下没有发现视频文件'.format(self.path))
              return
          else:
              self.logger.info('找到 {} 个视频文件'.format(l))
  
          for f in videofiles:
              self._history[f] = []
              self.pool.spawn(self._download, f)
          self.pool.join()
          self.logger.info('='*20 + '下载完成' + '='*20)
          for v, subs in self._history.items():
              basename = os.path.basename(v)
              self.logger.info(
                  '{}: 下载 {} 个字幕'.format(basename, len(subs)))
docs: SubFinder 入口，开始函数