public function __construct($invoice)
 {
     parent::__construct($invoice);
     $this->type = 'cancellation';
     $this->parent = false;
     if ($this->parent_id && get_post($this->parent_id)) {
         $this->set_parent($this->parent_id);
     }
 }
 public function __construct($invoice)
 {
     parent::__construct($invoice);
 }
 public function __construct($invoice)
 {
     parent::__construct($invoice);
     $this->type = 'packing_slip';
 }