redraw the legend

def draw_legend(self, show=None, auto_location=True, delay_draw=False):
        "redraw the legend"
        if show is not None:
            self.show_legend = show

        axes = self.canvas.figure.get_axes()
        # clear existing legend
        try:
            lgn = self.mpl_legend
            if lgn:
                for i in lgn.get_texts():
                    i.set_text('')
                for i in lgn.get_lines():
                    i.set_linewidth(0)
                    i.set_markersize(0)
                    i.set_marker('None')
                lgn.draw_frame(False)
                lgn.set_visible(False)
        except:
            pass

        labs = []
        lins = []
        for ax in axes:
            for xline in ax.get_lines():
                xlab = xline.get_label()
                if (xlab != '_nolegend_' and len(xlab)>0):
                    lins.append(xline)

        for l in lins:
            xl = l.get_label()
            if not self.show_legend: xl = ''
            labs.append(xl)
        labs = tuple(labs)

        lgn = axes[0].legend
        if self.legend_onaxis.startswith('off'):
            lgn = self.canvas.figure.legend
            # 'best' and 'off axis' not implemented yet
            if self.legend_loc == 'best':
                self.legend_loc = 'upper right'

        if self.show_legend:
            self.mpl_legend = lgn(lins, labs, prop=self.legendfont,
                                  loc=self.legend_loc)
            self.mpl_legend.draw_frame(self.show_legend_frame)
            if matplotlib.__version__ < '2.0':
                facecol = axes[0].get_axis_bgcolor()
            else:
                facecol = axes[0].get_facecolor()

            self.mpl_legend.legendPatch.set_facecolor(facecol)
            if self.draggable_legend:
                self.mpl_legend.draggable(True, update='loc')
            self.legend_map = {}
            for legline, legtext, mainline in zip(self.mpl_legend.get_lines(),
                                                  self.mpl_legend.get_texts(),
                                                  lins):
                legline.set_picker(5)
                legtext.set_picker(5)
                self.legend_map[legline] = (mainline, legline, legtext)
                self.legend_map[legtext] = (mainline, legline, legtext)
                legtext.set_color(self.textcolor)


        self.set_added_text_size()
        if not delay_draw:
            self.canvas.draw()