docs: def on_mouse_motion(self, widget, event):
          """selection on mouse over
  
          :param widget:
          :param Gdk.Event event: mouse motion event
          """
          path = self.view.get_path_at_pos(int(event.x), int(event.y))
          if path is not None:
              self.view.select_path(path)
          else:
              self.view.unselect_all()