code: def similarity(self, other: 'Trigram') -> float:
          
          if not len(self._trigrams) or not len(other._trigrams):
              return 0
  
          count = float(len(self._trigrams & other._trigrams))
          len1 = float(len(self._trigrams))
          len2 = float(len(other._trigrams))
  
          return count / (len1 + len2 - count)
docs: Compute the similarity with the provided other trigram.