[Fido]

Hi,
i'd like to start with programming plugins. I'd like to make first a simple window, but i make something wrong:
I have a file : window.lua - here a tried many variations.
At the moment it starts as follow

import "Turbine";
import "Turbine.UI";
import "Turbine.UI.Lotro";

Window = class( Turbine.UI.Lotro.GoldWindow );

function Window:Constructor()
Turbine.UI.Lotro.GoldWindow.Constructor( self );
...

Here I've copied the code from Turbine examples.
The I have a file : main.lua

import "Fido.simple.Window"
window = Window();
window:SetVisible(true);

and : simpleLotro.plugin

<?xml version="1.0"?>
<Plugin>
	<Information>
		<Name>simpleLotro</Name>
		<Author>Fido</Author>
		<Version>0.1</Version>
	</Information>
	<Package>Fido.simple.main</Package>
</Plugin>

But in game I get the error:

...d of the Rings Online\Plugins\Fido\simple\Window.lua:5: attempt to call global 'class' (a nil value)

I've tried with other Windows, but it is always the same error. What is the problem?
Thanks for help.
Fido