code: private function readChannelPackages($baseUrl)
      {
          $result = array();
  
          $xml = $this->requestXml($baseUrl, "/c/categories.xml");
          $xml->registerXPathNamespace('ns', self::ALL_CATEGORIES_NS);
          foreach ($xml->xpath('ns:c') as $node) {
              $categoryName = (string) $node;
              $categoryPackages = $this->readCategoryPackages($baseUrl, $categoryName);
              $result = array_merge($result, $categoryPackages);
          }
  
          return $result;
      }
docs: Read list of channel categories from
  {baseUrl}/c/categories.xml
  
  @param string $baseUrl
  @return PackageInfo[]