使用lambda函数在matplotlib中创建标记大小的自定义图例？

import matplotlib.pyplot as plt
import matplotlib.patches as mpatches

marker_func = lambda size: mpatches.Circle((0.5, 0.5), size)

legend_handles = [mpatches.Patch(label='Label 1', handler_map={mpatches.Circle: marker_func(10)}),
                  mpatches.Patch(label='Label 2', handler_map={mpatches.Circle: marker_func(20)}),
                  mpatches.Patch(label='Label 3', handler_map={mpatches.Circle: marker_func(30)})]

plt.plot([1, 2, 3], [4, 5, 6], 'r-', label='Data')
plt.legend(handles=legend_handles)
plt.show()