if not isinstance(source_list, list):
                 return
             for source in source_list:
             if not isinstance(source_list, list):
                 return
             for source in source_list:
                     continue
                 if source.get('type') == 'application/x-mpegURL' or determine_ext(video_url) == 'm3u8':
                     formats.extend(self._extract_m3u8_formats(
                     continue
                 if source.get('type') == 'application/x-mpegURL' or determine_ext(video_url) == 'm3u8':
                     formats.extend(self._extract_m3u8_formats(
                     continue
                 lang = try_get(cc, lambda x: x['locale']['locale'], compat_str)
                 sub_dict = (automatic_captions if cc.get('source') == 'auto'
                     continue
                 lang = try_get(cc, lambda x: x['locale']['locale'], compat_str)
                 sub_dict = (automatic_captions if cc.get('source') == 'auto'