public function metadata()
 {
     $gcurl = new Google_IO_Curl($this->client);
     $response = $gcurl->makeRequest(new Google_Http_Request("https://www.googleapis.com/analytics/v3/metadata/ga/columns"));
     //verify returned data
     $data = json_decode($response->getResponseBody());
     $items = $data->items;
     $data_items = [];
     $dimensions_data = [];
     $metrics_data = [];
     foreach ($items as $item) {
         if ($item->attributes->status == 'DEPRECATED') {
             continue;
         }
         if ($item->attributes->type == 'DIMENSION') {
             $dimensions_data[$item->attributes->group][] = $item;
         }
         if ($item->attributes->type == 'METRIC') {
             $metrics_data[$item->attributes->group][] = $item;
         }
     }
     //foreach
     $data_items['dimensions'] = $dimensions_data;
     $data_items['metrics'] = $metrics_data;
     return $data_items;
 }