docs: def end(self, folder=None):
          """End the simulation and destroy the current simulation environment.
          """
          ret = self.env.destroy(folder=folder)
          self._end_time = time.time()
          self._log(logging.DEBUG, "Simulation run with {} steps took {:.3f}s to"
                    " complete, while actual processing time was {:.3f}s."
                    .format(self.age, self._end_time - self._start_time,
                            self._processing_time))
          return ret