Parse raw sentence into ConllSentence

        Parameters
        ----------
        sentence : list
            a list of (word, tag) tuples

        Returns
        -------
        ConllSentence
            ConllSentence object

def parse(self, sentence):
        """Parse raw sentence into ConllSentence

        Parameters
        ----------
        sentence : list
            a list of (word, tag) tuples

        Returns
        -------
        ConllSentence
            ConllSentence object
        """
        words = np.zeros((len(sentence) + 1, 1), np.int32)
        tags = np.zeros((len(sentence) + 1, 1), np.int32)
        words[0, 0] = ParserVocabulary.ROOT
        tags[0, 0] = ParserVocabulary.ROOT
        vocab = self._vocab

        for i, (word, tag) in enumerate(sentence):
            words[i + 1, 0], tags[i + 1, 0] = vocab.word2id(word.lower()), vocab.tag2id(tag)

        with mx.Context(mxnet_prefer_gpu()):
            outputs = self._parser.forward(words, tags)
        words = []
        for arc, rel, (word, tag) in zip(outputs[0][0], outputs[0][1], sentence):
            words.append(ConllWord(id=len(words) + 1, form=word, pos=tag, head=arc, relation=vocab.id2rel(rel)))
        return ConllSentence(words)