code: def _add_colorbar(ax: Axes, cmap: colors.Colormap, cmap_data: np.ndarray, norm: colors.Normalize):
      
      fig = ax.get_figure()
      mappable = cm.ScalarMappable(cmap=cmap, norm=norm)
      mappable.set_array(cmap_data)   # TODO: Or what???
      fig.colorbar(mappable, ax=ax)
docs: Show a colorbar right of the plot.