WC_Connect_API_Client::get_labels_preview_pdf PHP Method

        public function get_labels_preview_pdf($request)
        {
            return $this->request('POST', 'shipping/labels/preview', $request);
        }

 public function get_item($request)
 {
     $raw_params = $request->get_params();
     $params = array();
     $params['paper_size'] = $raw_params['paper_size'];
     $this->settings_store->set_preferred_paper_size($params['paper_size']);
     $params['carrier'] = 'usps';
     $params['labels'] = array();
     foreach ($raw_params['captions'] as $caption) {
         $params['labels'][] = array('caption' => $caption);
     }
     $raw_response = $this->api_client->get_labels_preview_pdf($params);
     if (is_wp_error($raw_response)) {
         $this->logger->log($raw_response, __CLASS__);
         return $raw_response;
     }
     header('content-type: ' . $raw_response['headers']['content-type']);
     echo $raw_response['body'];
     die;
 }