Groupgridview Yii-Extension

Yii 1.1 Extensions
1

my view code is,

$this->widget(‘ext.groupgridview.GroupGridView’, array(

  'id' => 'grid1',


  'dataProvider' => $dataProvider,


  'extraRowColumns' => "hi",


  'extraRowExpression' => '"<b style=\"font-size: 3em; color: green\">ff</b>"',


  'columns'=>$columns,


));

it shows the following error

"Alias "ext.groupgridview.GroupGridView" is invalid. "

reference : http://groupgridview.demopage.ru/index.php?r=site/extrarow

help me to solve this