def draw_liver(liver, ax):
    ax.cla()
    ax = liver.plt_vtx(ax=ax)
    ax = liver.plt_x(ax=ax)
    plt_equal(ax)
    return ax
def draw_liver(liver, ax):
    ax.cla()
    ax = liver.plt_vtx(ax=ax)
    ax = liver.plt_x(ax=ax)
    plt_equal(ax)
    return ax