def get_sentence_boundaries(self):
        ys = [0]
        for x in self.sentences:
            y = ys[-1] + len(x)
            ys.append(y)
        return ys
Returns a list with the offsets in tokens where each sentence starts, in
dataset/ETHPy150Open machinalis/iepy/iepy/preprocess/stanford_preprocess.py/StanfordAnalysis.get_sentence_boundaries