[flexcomponents] error while extending button component

[learner]

Hi all,
I am trying to create a headerRenderer for Accordion..
and whenever I try to create class which extends a Button Class


package
{
    import mx.controls.Button;

    public class headerRenderer extends Button
    {
        public function headerRenderer()
        {
            super();
        }

    }
}


I get a error as : Interface method setFocus in namespace
mx.managers:IFocusManagerComponent is implemented with an incompatible
signature in class
??
can anybody explain me this ???????????/