def draw_footnote(fig, string, fontsize=9):
    """Draw footnote on a figure"""
    ax = fig.add_axes([0.0, 0.0, 1.0, 1.0])
    ax.text(0.5, 0.01, string, horizontalalignment='center', fontsize=fontsize)
    ax.patch.set_alpha(0.0)
    ax.set_axis_off()
    return ax
