code: def grab_focus(self):
          
          scene = self.get_scene()
          if scene and scene._focus_sprite != self:
              scene._focus_sprite = self
docs: grab window's focus. Keyboard and scroll events will be forwarded
          to the sprite who has the focus. Check the 'focused' property of sprite
          in the on-render event to decide how to render it (say, add an outline
          when focused=true)