ns affect the variations collection/list endpoint for the parent product.
	 *
	 * @param int|null $product_id The parent product ID, or null/0 to skip invalidation.
	 *
	 * @return void
	 */
	private function invalidate_variations_list( ?int $product_id ): void {
		if ( $product_id ) {
			wc_get_container()->get( VersionStringGenerator::class )->delete_version( "list_product_variations_{$product_id}" );
		}
	}
}