Compatibility with NLTK.
    Returns the cmudict lexicon as a dictionary, whose keys are
    lowercase words and whose values are lists of pronunciations.

def dict():
    """
    Compatibility with NLTK.
    Returns the cmudict lexicon as a dictionary, whose keys are
    lowercase words and whose values are lists of pronunciations.
    """
    default = defaultdict(list)
    for key, value in entries():
        default[key].append(value)
    return default