function _add_recipient_partner($emails, $objects)
 {
     $order_id = isset($objects->id) ? $objects->id : false;
     if ($order_id) {
         // change order currency
         if ($currency = get_post_meta($order_id, '_order_currency', true)) {
             TravelHelper::change_current_currency($currency);
         }
         $order = wc_get_order($order_id);
         if (sizeof($order->get_items()) > 0) {
             $partner_email_array = array();
             foreach ($order->get_items() as $item_id => $item) {
                 if (!empty($item['item_meta']['_st_st_booking_id'][0]) and $st_booking_id = $item['item_meta']['_st_st_booking_id'][0]) {
                     $post_type = !empty($item['item_meta']['_st_st_booking_post_type']) ? $item['item_meta']['_st_st_booking_post_type'] : false;
                     $post_type = st_wc_parse_order_item_meta($post_type);
                     $partner_email = apply_filters('st_get_owner_email_' . $post_type, $st_booking_id);
                     if ($partner_email != $st_booking_id) {
                         if (!in_array($partner_email, $partner_email_array)) {
                             $partner_email_array[] = $partner_email;
                         }
                     }
                 }
             }
             if (!empty($partner_email_array)) {
                 $emails .= ',' . implode(',', $partner_email_array);
             }
         }
     }
     return $emails;
 }