'Applies the tag method over a list of sentences. This method will return
for each sentence a list of tuples of (word, tag).'

def tag_sents(self, sentences):

    tagged_sents = super(SennaTagger, self).tag_sents(sentences)
    for i in range(len(tagged_sents)):
        for j in range(len(tagged_sents[i])):
            annotations = tagged_sents[i][j]
            tagged_sents[i][j] = (annotations['word'], annotations['pos'])
    return tagged_sents
