def _create_previous_pipes(self):
        """ Creates a target for each last-frame's pipe, any pipe starting
        with the prefix 'Previous::' has to be stored and copied each frame. """
        if self.previous_pipes:
            self._prev_stage = UpdatePreviousPipesStage(self.pipeline)
            for prev_pipe, prev_tex in iteritems(self.previous_pipes):

                if prev_pipe not in self.pipes:
                    self.error(
                        "Attempted to use previous frame data from pipe", prev_pipe,
                        "- however, that pipe was never created!"
                    )
                    return False

                # Tell the stage to transfer the data from the current pipe to
                # the current texture
                self._prev_stage.add_transfer(self.pipes[prev_pipe], prev_tex)
            self._prev_stage.create()
            self._prev_stage.set_dimensions()
            self.stages.append(self._prev_stage)
 Creates a target for each last-frame's pipe, any pipe starting
        with the prefix 'Previous::' has to be stored and copied each frame. 
metadrive/render_pipeline/rpcore/stage_manager.py