def get_viewer(self, v_id):
        """
        Get an existing viewer by viewer id.  If the viewer does not yet
        exist, make a new one.
        """
        try:
            return self.viewers[v_id]
        except KeyError:
            pass

        #  create top level window
        window = self.app.make_window(v_id % "Viewer %s", wid=v_id)

        # our own viewer object, customized with methods (see above)
        viewer = ImageViewer(self.logger, window)
        #viewer.url = window.url

        self.viewers[v_id] = viewer
        return viewer
dataset/ETHPy150Open ejeschke/ginga/ginga/web/pgw/ipg.py/ViewerFactory.get_viewer/swapped operands of `%`