code: def halt(self, checkpoint=None, finished=False, raise_error=True):
          
          self.stop_pipeline(PAUSE_FLAG)
          self._active = False
          if raise_error:
              raise PipelineHalt(checkpoint, finished)
docs: Stop the pipeline before completion point.
  
          :param str checkpoint: Name of stage just reached or just completed.
          :param bool finished: Whether the indicated stage was just finished
              (True), or just reached (False)
          :param bool raise_error: Whether to raise an exception to truly
              halt execution.