def from_serializable(cls, contents):
"""
Instantiate a ReviewVecotrizer from a serializable dictionary
Args:
contents (dict): the serializale dictionary
Returns:
an instance of the ReviewVectorizer class
"""
review_vocab = Vocabulary.from_serializable(contents['review_vocab'])
rating_vocab = Vocabulary.from_serializable(contents['rating_vocab'])
return cls(review_vocab=review_vocab, rating_vocab=rating_vocab)
