code: def add_url_rule(self, rule, endpoint=None, view_func=None, **options):
          
          if self.url_prefix:
              rule = self.url_prefix + rule
          options.setdefault('subdomain', self.subdomain)
          if endpoint is None:
              endpoint = _endpoint_from_view_func(view_func)
          defaults = self.url_defaults
          if 'defaults' in options:
              defaults = dict(defaults, **options.pop('defaults'))
          self.app.add_url_rule(rule, endpoint, view_func, defaults=defaults, **options)
docs: A helper method to register a rule (and optionally a view function)
          to the application.  The endpoint is automatically prefixed with the
          blueprint's name.