def create_highlight(self, artist):
        """Create a new highlight for the given artist."""
        highlight = copy.copy(artist)
        highlight.set(color=self.highlight_color, mec=self.highlight_color,
                      lw=self.highlight_width, mew=self.highlight_width)
        artist.axes.add_artist(highlight)
        return highlight
Create a new highlight for the given artist.