File: //var/www/html/ielts-store/wp-content/plugins/automatewoo/includes/Variables/Product_Parent_Sku.php
<?php
// phpcs:ignoreFile
namespace AutomateWoo;
if ( ! defined( 'ABSPATH' ) ) exit;
/**
 * @class Variable_Product_Parent_Sku
 * @since 2.9
 */
class Variable_Product_Parent_Sku extends Variable {
	function load_admin_details() {
		$this->description = __( "Displays the parent product's SKU.", 'automatewoo');
	}
	/**
	 * @param $product \WC_Product
	 * @param $parameters
	 * @return string
	 */
	function get_value( $product, $parameters ) {
		$parent_id = $product->get_parent_id();
		if ( $parent_id ) {
			$parent = wc_get_product( $parent_id );
			if ( $parent ) {
				return $parent->get_sku();
			}
		}
		return '';
	}
}