docs: @Nullable
    public static PasswordAuthentication requestProxyPasswordAuthentication (@Nullable final String sHostName,
                                                                             @Nullable final int nPort,
                                                                             @Nullable final String sProtocol)
    {
      return requestPasswordAuthentication (sHostName,
                                            (InetAddress) null,
                                            nPort,
                                            sProtocol,
                                            (String) null,
                                            (String) null,
                                            (URL) null,
                                            RequestorType.PROXY);
    }