private function get_node($node_id)
 {
     static $nodes = array();
     if (!isset($nodes[$node_id])) {
         $node = new midgardmvc_core_node();
         $node->get_by_id($node_id);
         $nodes[$node_id] = midgardmvc_core_providers_hierarchy_node_midgard2::get_instance($node);
     }
     return $nodes[$node_id];
 }