Too much itertools

    def __new__(cls, iterable=()):
        if isinstance(iterable, cls):
            return iterable
        iterable = frozenset(
            item for item in iterable if Conjunction() != item)
        for clause in iterable:
            assert isinstance(clause, Disjunction)
        bins = sorted((i, tuple(g)) for (i, g) in itertools.groupby(
            iterable, lambda clause: len(clause.terms)))
        output = frozenset()
        while bins:
            bin = bins.pop()
            intersections = ()
            non_compressed = set(bin[1])
            for fst, snd in itertools.combinations(bin[1], 2):
                diff = list(fst.terms.symmetric_difference(snd.terms))
                if (len(diff) == 2 and
                        Conjunction.cast(diff[0]) == not_(diff[1])):
                    intersections += Disjunction(
                        fst.terms.intersection(snd.terms)),
                    non_compressed.discard(fst)
                    non_compressed.discard(snd)
            output = output.union(non_compressed)
            if intersections:
                if bins and bins[-1][0] == bin[0] - 1:
                    bins[-1] = bins[-1][0], bins[-1][1] + intersections
                else:
                    bins.append((bin[0] - 1, intersections))
        return super().__new__(cls, output)