def _stop_index(self, stop_point, inclusive):
        """
        Determine index of stage of stopping point for run().

        :param str | pypiper.Stage | function stop_point: Stopping point itself
            or name of it.
        :param bool inclusive: Whether the stopping point is to be regarded as
            inclusive (i.e., whether it's the final stage to run, or the one
            just beyond)
        :return int: Index into sequence of Pipeline's stages that indicates
            where to stop; critically, the value of the inclusive parameter
            here is used to contextualize this index such that it's always
            returned as an exclusive stopping index (i.e., execute up to the
            stage indexed by the value returned from this function.)
        """
        if not stop_point:
            # Null case, no stopping point
            return len(self._stages)
        stop_name = parse_stage_name(stop_point)
        try:
            stop_index = self.stage_names.index(stop_name)
        except ValueError:
            raise UnknownPipelineStageError(stop_name, self)
        return stop_index + 1 if inclusive else stop_index