def lemmatize(ambiguous_word, pos=None, neverstem=False, 
              lemmatizer=wnl, stemmer=porter):
    if pos:
        lemma = lemmatizer.lemmatize(ambiguous_word, pos=pos)
    else:
        lemma = lemmatizer.lemmatize(ambiguous_word)
    stem = stemmer.stem(ambiguous_word)
    # Ensure that ambiguous word is a lemma.
    if not wn.synsets(lemma):
        if neverstem:
            return ambiguous_word
        if not wn.synsets(stem):
            return ambiguous_word
        else:
            return stem
    else:
     return lemma
Gives an approximation of the oldest revision.
dataset/ETHPy150Open alvations/pywsd/pywsd/utils.py/lemmatize--crossover with--dataset/ETHPy150Open edgewall/trac/tracopt/versioncontrol/svn/svn_fs.py/SubversionRepository.get_oldest_rev