如何制作具有无序值的第二个python x轴？

import matplotlib.pyplot as plt
import numpy as np

x1 = np.array([1, 2, 3, 4, 5])
y1 = np.array([10, 15, 7, 12, 8])

x2 = np.array([2, 4, 6, 8, 10])
y2 = np.array([5, 8, 6, 9, 4])

fig, ax1 = plt.subplots()
ax2 = ax1.twiny()  # 创建第二个x轴

ax1.plot(x1, y1, color='blue')
ax1.set_xlabel('X1', color='blue')
ax1.set_ylabel('Y1', color='blue')

ax2.plot(x2, y2, color='red')
ax2.set_xlabel('X2', color='red')

ax2.set_xlim(ax1.get_xlim())  # 让第二个x轴与第一个x轴的范围相同
ax2.set_xticks(x2)
ax2.set_xticklabels(['a', 'b', 'c', 'd', 'e'])

plt.show()