TranslatePress compatiblity hook

function pm_prepend_lang_prefix($base, $element) {
    global $TRP_LANGUAGE;

    if(!empty($TRP_LANGUAGE)) {
        $trp = TRP_Translate_Press::get_trp_instance();
        $trp_url_converter = $trp->get_component('url_converter');

        $trp_lang_code = $trp_url_converter->get_url_slug($TRP_LANGUAGE);
        $base = preg_replace("/(.*)(\/{$trp_lang_code})$/", "$1/{$trp_lang_code}", $base);
    }

    return $base;
}
add_filter('permalink_manager_filter_permalink_base', 'pm_prepend_lang_prefix', 9, 2);