code: def result(self) -> workflow.IntervalGeneratorType:
          
          config = cast(SentenceSegementationConfig, self.config)
  
          index = -1
          labels = None
  
          while True:
  
              # 1. Find the start of the sentence.
              start = -1
              while True:
                  # Check the ``labels`` generated from step (2).
                  if labels is None:
                      # https://www.python.org/dev/peps/pep-0479/
                      try:
                          index, labels = next(self.index_labels_generator)
                      except StopIteration:
                          return
                  # Check if we found a valid sentence char.
                  if labels[SentenceValidCharacterLabeler]:
                      start = index
                      break
                  # Trigger next(...) action.
                  labels = None
                  index = -1
  
              # 2. Find the ending.
              end = -1
              try:
                  while True:
                      index, labels = next(self.index_labels_generator)
  
                      # Detected invalid char.
                      if config.enable_strict_sentence_charset and \
                              not labels[SentenceValidCharacterLabeler] and \
                              not labels[WhitespaceLabeler]:
                          end = index
                          break
  
                      # Detected sentence ending.
                      if self._labels_indicate_sentence_ending(labels):
                          # Consume the ending span.
                          while True:
                              index, labels = next(self.index_labels_generator)
                              is_ending = (self._labels_indicate_sentence_ending(labels) or
                                           (config.extend_ending_with_delimiters and
                                            labels[DelimitersLabeler]))
  
                              if not is_ending:
                                  end = index
                                  break
                          # yeah we found the ending.
                          break
              except StopIteration:
                  end = len(self.input_sequence)
                  # Trigger next(...) action.
                  labels = None
                  index = -1
  
              yield start, end
docs: Generate intervals indicating the valid sentences.