code: def get_utt_regions(self):
          regions = []
          current_offset = 0
          for utt_idx in sorted(self.utt_ids):
              offset = current_offset
              num_frames = []
              refs = []
              for cnt in self.containers:
                  num_frames.append(cnt.get(utt_idx).shape[0])
                  refs.append(cnt.get(utt_idx, mem_map=True))
              if len(set(num_frames)) != 1:
                  raise ValueError('Utterance {} has not the same number of frames in all containers!'.format(utt_idx))
              num_chunks = math.ceil(num_frames[0] / float(self.frames_per_chunk))
              region = (offset, num_chunks, refs)
              regions.append(region)
              current_offset += num_chunks
          return regions