docs: def enable_grid(self, show=None, delay_draw=False):
          "enable/disable grid display"
          if show is not None:
              self.show_grid = show
          axes = self.canvas.figure.get_axes()
          ax0 = axes[0]
          for i in ax0.get_xgridlines() + ax0.get_ygridlines():
              i.set_color(self.gridcolor)
              i.set_zorder(-1)
          axes[0].grid(self.show_grid)
          for ax in axes[1:]:
              ax.grid(False)
          if not delay_draw:
              self.canvas.draw()