docs: def add_static_url(self, url_path, directory, endpoint=None, roles=None):
          """Add a new url rule for static files.
  
          :param url_path: subpath from application static url path. No heading
              or trailing slash.
          :param directory: directory to serve content from.
          :param endpoint: flask endpoint name for this url rule.
  
          Example::
  
             app.add_static_url('myplugin',
                                '/path/to/myplugin/resources',
                                endpoint='myplugin_static')
  
          With default setup it will serve content from directory
          `/path/to/myplugin/resources` from url `http://.../static/myplugin`
          """
          url_path = self.static_url_path + "/" + url_path + "/<path:filename>"
          self.add_url_rule(
              url_path,
              endpoint=endpoint,
              view_func=partial(send_file_from_directory, directory=directory),
              roles=roles,
          )
          self.add_access_controller(
              endpoint, allow_access_for_roles(Anonymous), endpoint=True
          )