protected function subscribeGraphsystem(): void
    {
        $this->kernel->events()->on('graphsystem.touched',  
            function(array $var) {
                $this->index($var);
            })
            ->on('graphsystem.node_deleted',  
            function(string $id) {
                $this->nodeDeleted($id);
            })
            ->on('graphsystem.edge_deleted',  
            function(string $id) {
                $this->edgeDeleted($id);
            }
        );
    }