public function resetAllPropertiesExcept($properties=array())
  {
    foreach ($this->obj_to_db_trans as $obj_prop => $db_field) {
      if(  !in_array($obj_prop,$this->key_properties) && !in_array($obj_prop,$properties) ){
        $this->{$obj_prop}=null;
      }
    }
  }