[Moo] Implement: How to access parent function?

[Korbinian Moser]

Hi, I want to implement a step event to the Fx base class. 
Sadly, this doesn't work:

    Fx.implement(
    {
        step: function(now)
        {
            this.parent.step(now);
            this.fireEvent( 'step');
        }
    });

Doing it that way, this.parent is undefined. 
Taking the original function from an instance causes an endless loop of 
implementations. 
Is there a way to access the original function without copying all its code 
here?