def __matches(s1, s2, ngrams_fn, n=3):
    """
        Returns the n-grams that match between two sequences

        See also: SequenceMatcher.get_matching_blocks

        Args:
            s1: a string
            s2: another string
            n: an int for the n in n-gram

        Returns:
            set:
    """
    ngrams1, ngrams2 = set(ngrams_fn(s1, n=n)), set(ngrams_fn(s2, n=n))
    return ngrams1.intersection(ngrams2)
