private function get_relational_model($obj, $model_from_info)
 {
     if (!$model_from_info) {
         return false;
     }
     if (is_array($model_from_info)) {
         foreach ($model_from_info as $value_from => $type) {
             if ($type == 'model') {
                 $model_from = $value_from;
                 break;
             } elseif ($type == 'timeline_related_table') {
                 if (empty($obj->{$value_from})) {
                     return false;
                 }
                 $namespace = \Timeline\Site_Util::get_namespace4foreign_table($obj->{$value_from});
                 $model_from = \Util_Orm::get_model_name($obj->{$value_from}, $namespace);
             }
         }
     } else {
         $model_from = $model_from_info;
     }
     return $model_from;
 }