/**
  * Generates Global Property ID if it does not exist
  *
  * @param bool $property_id
  *
  * @return string | Returns GPID
  * @since 1.6
  */
 public static function maybe_set_gpid($property_id = false)
 {
     if (!$property_id) {
         return false;
     }
     $exists = get_post_meta($property_id, 'wpp_gpid', true);
     if ($exists) {
         return $exists;
     }
     $gpid = WPP_F::get_gpid($property_id, true);
     update_post_meta($property_id, 'wpp_gpid', $gpid);
     return $gpid;
 }