code: def __similarity(s1, s2, ngrams_fn, n=3):
      
      ngrams1, ngrams2 = set(ngrams_fn(s1, n=n)), set(ngrams_fn(s2, n=n))
      matches = ngrams1.intersection(ngrams2)
      return 2 * len(matches) / (len(ngrams1) + len(ngrams2))
docs: The fraction of n-grams matching between two sequences
  
          Args:
              s1: a string
              s2: another string
              n: an int for the n in n-gram
  
          Returns:
              float: the fraction of n-grams matching