Modify data before it is drawn out by the geom

        Parameters
        ----------
        layers : list
            List of layers

def finish_data(self, layers):
        """
        Modify data before it is drawn out by the geom

        Parameters
        ----------
        layers : list
            List of layers
        """
        for layer in layers:
            layer.data = self.facet.finish_data(layer.data, self)