import string


def _lower_and_clean_captions(captions):
    """Lower case and delete punctuation"""
    table = str.maketrans("", "", string.punctuation)
    for _, caption_list in captions.items():
        for i in range(len(caption_list)):
            caption = caption_list[i]
            caption = caption.split()
            caption = [word.lower() for word in caption]
            caption = [w.translate(table) for w in caption]
            caption_list[i] = " ".join(caption)
    return captions