code: def activate(self, page=None):
          
          page = page or ''
  
          if '://' in page:
              self._iface.activate_overlay_url(page)
  
          else:
              self._iface.activate_overlay_game(page)
docs: Activates overlay with browser, optionally opened at a given page.
  
          :param str page: Overlay page alias (see OVERLAY_PAGE_*)
              or a custom URL.