ShipmentPackageCreationInterface.php

<?php
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
namespace Magento\Sales\Api\Data;

/**
 * Shipment package interface.
 *
 * A shipment is a delivery package that contains products. A shipment document accompanies the shipment. This
 * document lists the products and their quantities in the delivery package.
 * @api
 * @since 100.1.2
 */
interface ShipmentPackageCreationInterface extends \Magento\Framework\Api\ExtensibleDataInterface
{
    /**
     * Retrieve existing extension attributes object or create a new one.
     *
     * @return \Magento\Sales\Api\Data\ShipmentPackageCreationExtensionInterface|null
     * @since 100.1.2
     */
    public function getExtensionAttributes();

    /**
     * Set an extension attributes object.
     *
     * @param \Magento\Sales\Api\Data\ShipmentPackageCreationExtensionInterface $extensionAttributes
     * @return $this
     * @since 100.1.2
     */
    public function setExtensionAttributes(
        \Magento\Sales\Api\Data\ShipmentPackageCreationExtensionInterface $extensionAttributes
    );
}