public function unpublish($preBill)
 {
     if ($preBill instanceof PreBillModel) {
         $mapper = PreBillMapper::getInstance();
         $result = $mapper->unpublish($preBill->getId());
         if ($result) {
             \App::audit('Unpublished prebill with Id ' . $preBill->getId(), $preBill);
             return $result;
         }
     } else {
         throw new AppEx\ValidateException('Invalid prebill');
     }
 }
 protected function setUp()
 {
     parent::setUp();
     $this->_mapper = \Application\Model\Mapper\PreBillMapper::getInstance();
 }