docs: def relabel(self, xlabel=None, ylabel=None,
                  y2label=None, title=None, delay_draw=False):
          " re draw labels (title, x, y labels)"
          n = self.labelfont.get_size()
          self.titlefont.set_size(n+1)
          # print("  plot relabel ", delay_draw)
          rcParams['xtick.labelsize'] =  rcParams['ytick.labelsize'] =  n
          rcParams['xtick.color'] =  rcParams['ytick.color'] =  self.textcolor
  
          if xlabel is not None:
              self.xlabel = xlabel
          if ylabel is not None:
              self.ylabel = ylabel
          if y2label is not None:
              self.y2label = y2label
          if title is not None:
              self.title = title
  
          axes = self.canvas.figure.get_axes()
          kws = dict(fontproperties=self.titlefont, color=self.textcolor)
          axes[0].set_title(self.title, **kws)
          kws['fontproperties'] = self.labelfont
  
          if len(self.xlabel) > 0 and self.xlabel not in ('', None, 'None'):
              axes[0].set_xlabel(self.xlabel, **kws)
  
          if len(self.ylabel) > 0 and self.ylabel not in ('', None, 'None'):
              axes[0].set_ylabel(self.ylabel, **kws)
          if (len(axes) > 1 and len(self.y2label) > 0 and
              self.y2label not in ('', None, 'None')):
              axes[1].set_ylabel(self.y2label, **kws)
  
          for ax in axes[0].xaxis, axes[0].yaxis:
              for t in (ax.get_ticklabels() + ax.get_ticklines()):
                  t.set_color(self.textcolor)
                  if hasattr(t, 'set_fontsize'):
                      t.set_fontsize(n)
  
          self.set_added_text_size()
          if self.mpl_legend is not None:
              for t in self.mpl_legend.get_texts():
                  t.set_color(self.textcolor)
          if not delay_draw:
              self.canvas.draw()