PayPal\Api\Refund::setParentPayment PHP Method

    public function setParentPayment($parent_payment)
    {
        $this->parent_payment = $parent_payment;
        return $this;
    }

 public static function createRefund()
 {
     $refund = new Refund();
     $refund->setCreateTime(self::$createTime);
     $refund->setAmount(AmountTest::createAmount());
     $refund->setCaptureId(self::$captureId);
     $refund->setId(self::$id);
     $refund->setLinks(array(LinksTest::getObject()));
     $refund->setParentPayment(self::$parentPayment);
     return $refund;
 }