private function _convert($feature, $to)
 {
     $feature_id = $feature['id'];
     // change only multiple/selectable flags
     if ($to['type'] == $feature['type']) {
         $this->feature_model->updateById($feature_id, array('multiple' => $to['multiple'], 'selectable' => $to['selectable']));
     } else {
         // get all features values
         $values = $this->getValues($feature, $to);
         // change type of feature (with removing old values)
         $feature = $this->changeType($feature, $to);
         // reset values taking into account new type
         $new_values = $this->setValues($feature, $values);
         // bind new values to products
         $this->bindToProducts($feature, $new_values);
     }
 }