def METHOD_NAME(self, stemmer_mode, expected_stems):
    stemmer = PorterStemmer(mode=stemmer_mode)
    for word, true_stem in zip(self._vocabulary(), expected_stems):
        our_stem = stemmer.stem(word)
        assert (
            our_stem == true_stem
        ), "{} should stem to {} in {} mode but got {}".format(
            word,
            true_stem,
            stemmer_mode,
            our_stem,
        )