code: def _filter_path(self, path):
          
          if self._is_videofile(path):
              return [path, ]
  
          if os.path.isdir(path):
              result = []
              for root, dirs, files in os.walk(path):
                  result.extend(filter(self._is_videofile, map(
                      lambda f: os.path.join(root, f), files)))
              return result
          else:
              return []
docs: 筛选出 path 目录下所有的视频文件