function __construct($input = [], $flags = 0, $iterator_class = Shipwire::ITERATOR)
 {
     parent::__construct($input, $flags, $iterator_class);
 }
 function __construct($input = [], $flags = 0, $iterator_class = Shipwire::ITERATOR)
 {
     $_filtered = ['sku' => strval($input['sku']), 'quantity' => intval($input['quantity'])];
     parent::__construct($_filtered, $flags, $iterator_class);
 }