/**
  * @param File $file
  */
 protected function removeFilesRecursively(Folder $file)
 {
     if ($file->hasChildren()) {
         foreach ($file->getChildren() as $childFile) {
             if ($childFile instanceof Folder) {
                 $this->removeFilesRecursively($childFile);
             } else {
                 $this->removeSingleFile($childFile);
             }
         }
     }
     $this->removeSingleFile($file);
 }