bookingpress_{payment_gateway}_apply_refund

    add_filter('bookingpress_{payment_gateway}_apply_refund', 'bookingpress_{payment_gateway}_apply_refund_func', 10, 2);
    //{payment_gateway} is dynamic text, it replaces with the actual payment gateway slug like (paypal, stripe)
    function bookingpress_{payment_gateway}_apply_refund_func($response, $bookingpress_send_refund_data)
    {
        //$response response data array from payment gateway
        //$bookingpress_send_refund_data passing data to the payment gateway

        return $response;
    }