function initializeAggregateFeed($id, $file_name)
   {
       parent::initializeAggregateFeed($id, $file_name);
       $content = '<?xml version="1.0" encoding="UTF-8" ?>
 <products>';
       file_put_contents($this->filename, $content);
   }
 function initializeAggregateFeed($id, $file_name)
 {
     parent::initializeAggregateFeed($id, $file_name);
     //Erase file
     $content = '';
     file_put_contents($this->filename, $content);
 }