def tfidf_vectorize(words,tfidf):
    """
    Vectorizes text using a Term Frequency-Inverse Document Frequency model

    Parameters
    ----------
    words : str
        A review document (a string containing one or more reviews)
    tfidf : sklearn.TfidfVectorizer
        A vectorizer that takes a list of strings as input documents

    Returns
    -------
    numpy.array
        An array containing TF-IDF values for the input review document

    """
    return tfidf.transform([words])