Lemmas are 'Form' objects

Question

I am trying to find average differences in sentiment for all antonyms in synsets using the function

def check_antonym_similar(wnd, senti):
    """
    find the average difference for all synsets that have antonyms
    and which have non-zero sentiment
    """
    diffs = []
    ## look at all the synsets we have sentiment for
    for ssid1 in senti:
        ss1 = wnd.synset(id=ssid1)  # get the synset
        for lemma in ss1.lemmas():  # get lemmas
            # Find antonyms for each lemma
            for antonym in lemma.antonyms():
                ssid2 = antonym.synset().id
                ## check if we have sentiment for the antonym
                if (ssid2 in senti) \
                   and senti[ssid2] != 0.0 and senti[ssid1] != 0.0:
                    ## keep only non-zero sentiments
                    diff = abs(senti[ssid2] - senti[ssid1])
                    diffs.append(diff)
    if len(diffs) > 0:
        return sum(diffs)/len(diffs)
    else:
        return 0.0

antonym_diff = check_antonym_similar(ewn, ss_senti)
print(f"Average difference in non-zero sentiment for antonyms {antonym_diff:.2f}")

When I checked the types using

for ssid in list(ss_senti.keys())[:5]:
    ss = ewn.synset(id=ssid)  # get the synset
    lemmas = ss.lemmas()  # get lemmas
    for lemma in lemmas:
        print(f"Lemma: {lemma}, Type: {type(lemma)}")

It did prove that the lemmas in wd are wd.Forms making them not unusable with .antonyms()

Is there some change in WordNet causing this problem? I wasn't able to find anything in the documentation nor did it even mention antonyms at all.