Fetching current Transposh languge for Booking plugin

Hi all – I am using the plugin Booking Systems Pro and include a reservation form on several pages with a shortcode. The form is not being translated by Transposh and not following Transposh’s current language – it’s always in English or in the language I tell it to be in the shortcode. Can someone tell me how to instruct the shortcode to following the site’s current language?

if (array_key_exists('lang', $atts)){
                    $language = $atts['lang'];
                }
                else{
                    $language = 'en'; // instead of 'en' I want Transposh's current language.
                }

Thanks!