/**
  * @param string $id
  * @return User|null
  */
 public function getUser($id)
 {
     try {
         $cfUser = $this->cultureFeed->getUser($id, self::INCLUDE_PRIVATE_FIELDS);
         // Cast to a User object that can be safely encoded to json.
         return User::fromCultureFeedUser($cfUser);
     } catch (\CultureFeed_ParseException $e) {
         return null;
     }
 }