public function withTags($tags)
 {
     if ($tags) {
         $taggings = TagTable::getTaggings($tags, array('model' => $this->_model));
         $cmp_tags = isset($taggings[$this->_model]) ? $taggings[$this->_model] : array(0);
         $this->andWhereIn('i.id', $cmp_tags);
     }
     return $this;
 }