Not finding an attr and generating attr-defined error

Bug Report
Generates a [attr-defined] error claiming the attr doesnot exists.

To Reproduce

import pandas as pd
tmp_df = pd.DataFrame(data={
    "c1": [1, 2, 3, 4],
    "c2": [5, 6, 7, 8]
})
    
if any(tmp_df.index.diff()[1:] <= 0):
    print("ohoh")

Expected Behavior
No error should be produced

Actual Behavior

error: "Index[Any]" has no attribute "diff"  [attr-defined]
        if any(tmp_df.index.diff()[1:] <= 0):
               ^~~~~~~~~~~~~~~~~

Your Environment
python=3.11
pandas
pandas-stubs

首先使用 pandas 和 pandas-stubs 运行提供的 Python 3.11 复现代码，然后检查为什么 tmp_df.index 的类型是 Index[Any]，而不是暴露 diff()。完成的标准是：有效调用不再产生 attr-defined 错误，并且该复现由回归测试覆盖。