# deeplabcut.extract_frames, lines 269-272
    if videos_list is None:
        videos = cfg.get("video_sets_original") or cfg["video_sets"]
    else:  # filter video_list by the ones in the config file
        videos = [v for v in cfg["video_sets"] if v in videos_list]  # none of videos_list are in cfg["video_sets"] yet!
    ...

    has_failed = []
    for video in videos:
        ...

    if all(has_failed):  # True as the list is empty
        print("Frame extraction failed. Video files must be corrupted.")