如何检查pandas MultiIndex中是否存在列

import pandas as pd

# 创建一个包含 MultiIndex 的 DataFrame
df = pd.DataFrame({'A': [1, 2, 3],
                   'B': [4, 5, 6],
                   'C': [7, 8, 9]},
                  index=pd.MultiIndex.from_tuples([('Group1', 'Index1'),
                                                  ('Group1', 'Index2'),
                                                  ('Group2', 'Index3')],
                                                 names=['Group', 'Index']))

# 检查 'A' 列是否存在于 MultiIndex 中
if 'A' in df.columns:
    print("Column 'A' exists in MultiIndex.")
else:
    print("Column 'A' does not exist in MultiIndex.")

# 检查多个列是否存在于 MultiIndex 中
columns_to_check = ['A', 'B', 'D']
for column in columns_to_check:
    if column in df.columns:
        print(f"Column '{column}' exists in MultiIndex.")
    else:
        print(f"Column '{column}' does not exist in MultiIndex.")