/**
  * injecting shipment data into order shipment tracking collection
  * @param array $data
  * @return self
  */
 protected function _injectShipmentTracks(array $data)
 {
     if (!$this->_tracks) {
         $this->_tracks = new Varien_Data_Collection();
     }
     $this->_tracks->addItem($this->factory->getNewSalesOrderShipmentTrack($data));
     return $this;
 }