code: def register_assets(self):
          
          self.blueprint.add_url_rule(
              # Register another path to ensure assets compatibility
              "{0}.secondary/<filetype>/<asset>".format(self.static_url_path),
              view_func=self.r_assets,
              endpoint="secondary_assets",
              methods=["GET"]
          )
docs: Merge and register assets, both as routes and dictionary
  
          :return: None