/**
  * delete all items and items' attributes from recommender
  *
  */
 public function clear(DataApi\Client $client)
 {
     if (!$this->config->isAppend()) {
         $client->deleteItems();
         $itemsAttributes = $client->getItemsAttributes();
         if (isset($itemsAttributes['attributes'])) {
             foreach ($itemsAttributes['attributes'] as $attribute) {
                 $client->deleteItemsAttribute($attribute['name']);
             }
         }
     }
     return $this;
 }