'Construct a TrigramCollocationFinder for all trigrams in the given
sequence.'

@classmethod
def from_words(cls, words, window_size=3):

    if (window_size < 3):
        raise ValueError('Specify    window_size    at    least    3')
    wfd = FreqDist()
    wildfd = FreqDist()
    bfd = FreqDist()
    tfd = FreqDist()
    for window in ngrams(words, window_size, pad_right=True):
        w1 = window[0]
        if (w1 is None):
            continue
        for (w2, w3) in _itertools.combinations(window[1:], 2):
            wfd[w1] += 1
            if (w2 is None):
                continue
            bfd[(w1, w2)] += 1
            if (w3 is None):
                continue
            wildfd[(w1, w3)] += 1
            tfd[(w1, w2, w3)] += 1
    return cls(wfd, bfd, wildfd, tfd)
