code: def split_sentences(self):
          
          from pyrouge.utils.sentence_splitter import PunktSentenceSplitter
          self.log.info("Splitting sentences.")
          ss = PunktSentenceSplitter()
          sent_split_to_string = lambda s: "\n".join(ss.split(s))
          process_func = partial(
              DirectoryProcessor.process, function=sent_split_to_string)
          self.__process_summaries(process_func)
docs: ROUGE requires texts split into sentences. In case the texts
          are not already split, this method can be used.