public function add_coupon( $code = array(), $discount = 0, $discount_tax = 0 ) {
		wc_deprecated_function( 'WC_Order::add_coupon', '3.0', 'a new WC_Order_Item_Coupon object and add to order with WC_Order::add_item()' );

		$item = new WC_Order_Item_Coupon();
		$item->set_props( array(
			'code'         => $code,
			'discount'     => $discount,
			'discount_tax' => $discount_tax,
			'order_id'     => $this->get_id(),
		) );
		$item->save();
		$this->add_item( $item );
		wc_do_deprecated_action( 'woocommerce_order_add_coupon', array( $this->get_id(), $item->get_id(), $code, $discount, $discount_tax ), '3.0', 'woocommerce_new_order_item action instead.' );
		return $item->get_id();
	}