def legend_aesthetics(self, layer, plot):
        """
        Return the aesthetics that contribute to the legend

        Parameters
        ----------
        layer : Layer
            Layer whose legend is to be drawn
        plot : ggplot
            Plot object

        Returns
        -------
        matched : list
            List of the names of the aethetics that contribute
            to the legend.
        """
        l = layer
        legend_ae = set(self.key.columns) - {'label'}
        all_ae = (l.mapping.keys() |
                  (plot.mapping if l.inherit_aes else set()) |
                  l.stat.DEFAULT_AES.keys())
        geom_ae = l.geom.REQUIRED_AES | l.geom.DEFAULT_AES.keys()
        matched = all_ae & geom_ae & legend_ae
        matched = list(matched - set(l.geom.aes_params))
        return matched
Return the aesthetics that contribute to the legend

        Parameters
        ----------
        layer : Layer
            Layer whose legend is to be drawn
        plot : ggplot
            Plot object

        Returns
        -------
        matched : list
            List of the names of the aethetics that contribute
            to the legend.