Compute the similarity with the provided other trigram.

def similarity(self, other: 'Trigram') -> float:
        """
        Compute the similarity with the provided other trigram.
        """
        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)