code: public function folders()
      {
          if (!$this->folders instanceof FoldersController) {
              $this->folders = new FoldersController($this->getClient(), $this->cachePolicy, $this->cache);
              $this->folders->setLogger($this->logger);
          }
  
          return $this->folders;
      }
docs: Folders are used to group Media in a hierarchial manner.
  
  @return FoldersController