def evaluate_sentence(self, n, tokens, display=True):
        """
        Get the probability for this sentence

        Args:
            n (int): max ngram order to use
            tokens (list(str)): Sentence
        """
        grams = zip(*[tokens[i:] for i in range(n)])

        p = 1
        for gram in grams:
            if n == 1 and gram[0] == "<s>":
                continue

            if gram in self.ngrams[n]:
                p *= self.ngrams[n][gram]
                if display:
                    self._pretty_print(gram, p)

            else:
                s = 1
                keys = set()
                keys_h = set()
                for k, v in self.ngrams[n].items():
                    if k[0] == gram[0]:
                        s -= v
                        keys_h.add(k[1])
                    else:
                        keys.add(k[1])

                keys = keys - keys_h
                gram = list(gram[1:])
                pbo = 0
                for k in keys:
                    pbo += self.evaluate_sentence(n-1, [k], display=False)

                l = s / pbo
                p *= l * self.evaluate_sentence(n-1, gram, display=True)
        return p

    def _pretty_print(self, gram, p):
        if len(gram) == 1:
            print('P_bo({}) = {}'.format(gram[0], p))
        else:
            print('P_bo({} | {}) = {}'.format(gram[-1], ' '.join(gram[:len(gram)-1]), p))