def redraw_layer(self,name):
        """
        Redraws the given layer.
        
        :raises ValueError: If there is no Layer with the given name.
        """
        if name not in self._layers:
            raise ValueError("Layer %s not part of widget, cannot redraw")
        self._layers[name].on_redraw()
Redraws the given layer.
        
        :raises ValueError: If there is no Layer with the given name.