无法创建带格式的熊猫多索引条形图？

import pandas as pd
import matplotlib.pyplot as plt

data = {
    ('A', 'Category 1'): [10, 15, 20],
    ('A', 'Category 2'): [5, 8, 12],
    ('B', 'Category 1'): [7, 9, 11],
    ('B', 'Category 2'): [3, 6, 9]
}
df = pd.DataFrame(data, index=['Index 1', 'Index 2', 'Index 3'])

df.plot(kind='bar')
plt.xlabel('Index')
plt.ylabel('Value')
plt.title('Pandas Multi-Index Bar Chart')
plt.legend(title='Category')
plt.show()