@classmethod
    def from_words(cls, words, window_size=4):
        if 4 < window_size:
            raise ValueError("Specify window_size at least 4")
        ixxx = FreqDist()
        iiii = FreqDist()
        ii = FreqDist()
        iii = FreqDist()
        ixi = FreqDist()
        ixxi = FreqDist()
        iixi = FreqDist()
        ixii = FreqDist()

        for window in ngrams(words, window_size, pad_right=True):
            w1 = window[0]
            if w1 is None:
                continue
            for w2, w3, w4 in _itertools.combinations(window[1:], 3):
                ixxx[w1] += 1
                if w2 is None:
                    continue
                ii[(w1, w2)] += 1
                if w3 is None:
                    continue
                iii[(w1, w2, w3)] += 1
                ixi[(w1, w3)] += 1
                if w4 is None:
                    continue
                iiii[(w1, w2, w3, w4)] += 1
                ixxi[(w1, w4)] += 1
                ixii[(w1, w3, w4)] += 1
                iixi[(w1, w2, w4)] += 1

        return cls(ixxx, iiii, ii, iii, ixi, ixxi, iixi, ixii)
dataset/ETHPy150Open nltk/nltk/nltk/collocations.py/QuadgramCollocationFinder.from_words/swapped operands of `<`