code: function(o) {
          var i, Y = this,
              core = [],
              mods = YUI.Env.mods,
              extras = Y.config.core || [ 'get', 
                                          'rls', 
                                          'intl-base', 
                                          'loader', 
                                          'yui-log', 
                                          'yui-later', 
                                          'yui-throttle' ];
  
          for (i=0; i<extras.length; i++) {
              if (mods[extras[i]]) {
                  core.push(extras[i]);
              }
          }
  
          Y._attach(['yui-base']);
          Y._attach(core);
  
      }
docs: Finishes the instance setup. Attaches whatever modules were defined
  when the yui modules was registered.
  @method _setup
  @private