old_contents: Fire.JS.get(Fire, '$0', function () {
      var selection = Editor.Selection.curSelection('node');
      if (selection.length > 0) {
          var id = selection[0];
          var node = Fire.engine.getInstanceById(id);
          return node;
      }
  });
  
  Fire.JS.get(Fire, '$s', function () {
      return Fire.engine.getCurrentScene();
  });
  
new_contents: Fire.JS.get(Fire, '$0', function () {
      var selection = Editor.Selection.curSelection('node');
      if (selection.length > 0) {
          var id = selection[0];
          var node = Fire.engine.getInstanceById(id);
          return node;
      }
  });
  
  Fire.JS.get(Fire, '$0N', function () {
      var wrapper = Fire.$0;
      if (wrapper) {
          return wrapper.targetN;
      }
  });
  
  Fire.JS.get(Fire, '$s', function () {
      return Fire.engine.getCurrentScene();
  });
  
  Fire.JS.get(Fire, '$S', function () {
      return Fire.engine.getCurrentScene();
  });
  
  Fire.JS.get(Fire, '$SN', function () {
      return Fire.engine.getCurrentSceneN();
  });
  
subject: add Fire.$0N and Fire.$SN