code: public function getUnmappedLocalKeys()
      {
          $u = array_diff(array_keys($this->localModel->getMetaData()->columns), array_keys($this->_map));
          unset($u[$this->localPrimaryKeyName]);
  
          return $u;
      }
docs: Get unmapped local keys.
  
  @return [[@doctodo return_type:getUnmappedLocalKeys]] [[@doctodo return_description:getUnmappedLocalKeys]]