如何在matplot中绘制比例不变的直角标签

import matplotlib.pyplot as plt

# 创建一个示例数据
labels = ['A', 'B', 'C', 'D']
sizes = [15, 30, 45, 10]

# 绘制饼图
fig, ax = plt.subplots()
ax.pie(sizes, labels=labels, autopct='%1.1f%%')

# 添加直角标签
for i, label in enumerate(labels):
    angle = sum(sizes[:i]) + sizes[i] / 2
    x = 0.5 * 0.75 * plt.cos(0.5 * plt.pi - plt.pi * angle / 180)
    y = 0.5 * 0.75 * plt.sin(0.5 * plt.pi - plt.pi * angle / 180)
    ax.annotate(label, (x, y), xytext=(1.2*x, 1.2*y), ha='center', va='center')

# 设置图形的比例和标题
ax.axis('equal')
plt.title('Proportional Labels in Matplotlib')

# 显示图形
plt.show()