/**
  * Retrieves a pseudo roster based off of a registration.
  *
  * @param jid To retrieve the roster for.
  * @param type TransportType the roster is for.
  * @return A Pseudo roster
  * @throws UserNotFoundException if the user is not actually registered.
  */
 public PseudoRoster getPseudoRoster(JID jid, TransportType type) throws UserNotFoundException {
   Collection<Registration> registrations =
       RegistrationManager.getInstance().getRegistrations(jid, type);
   if (registrations.isEmpty()) {
     // User is not registered with us.
     throw new UserNotFoundException("Unable to find registration.");
   }
   Registration registration = registrations.iterator().next();
   return getPseudoRoster(registration);
 }