public function addFile(File $file)
 {
     $id = $file->getId();
     $path = new \stdClass();
     $path->path = $file->getPath();
     $path->siteId = $file->getSiteId();
     $path->siteName = $file->getSiteName();
     $psi_std = new \stdClass();
     $psi_std->id = $id;
     $psi_std->path = $path;
     $psi_std->type = File::TYPE;
     $psi_std->recycled = false;
     $this->files[] = new p\PublishableAssetIdentifier($psi_std);
     return $this;
 }