def _perform_update(self):
        """ Collects all entries, extracts their images and re-renders the
        window """

        # Collect texture stages
        self._stages = []
        for entry in sorted(self.entries, key=lambda entry: entry.sort):
            if isinstance(entry, Texture):
                if self._display_images:
                    self._stages.append(entry)
            # Can not use isinstance or we get circular import references
            elif entry.__class__.__name__ == "RenderTarget":
                for target in itervalues(entry.targets):
                    self._stages.append(target)
            else:
                self.warn("Unrecognized instance!", entry.__class__)

        self._render_stages()
 Collects all entries, extracts their images and re-renders the
        window 
metadrive/render_pipeline/rpcore/gui/buffer_viewer.py