public function getChild($name)
 {
     $path = $this->path . '/' . $name;
     if (!M::file_exists($path)) {
         throw new Sabre_DAV_Exception_NotFound('File with name ' . $path . ' could not be located');
     }
     if (M::is_dir($path)) {
         return new MongoDirectory($path);
     } else {
         return new MongoFile($path);
     }
 }