def _get_top_words(model, feature_names, n_top_words=40):
    """ Return top forty words from each topic in trained topic model.
    """
    topic_words = []
    for topic in model.components_:
        top_words = [feature_names[i] for i in topic.argsort()[:-n_top_words-1:-1]]
        topic_words += [top_words]
    return topic_words