TL;DR: statsmodels removed its Appender shim. Import it from `pandas.util._decorators` instead, or upgrade the package that does the old import.

## The error
```text
ImportError: cannot import name 'Appender' from 'statsmodels.compat.pandas'
```

## Fix it
1. Replace the import in your code:
   ```python
   from pandas.util._decorators import Appender
   ```
   Expected: no import error; Appender behaves the same.
2. If the bad import is inside a third-party package, upgrade that package:
   ```
   pip install -U [the-package]
   ```
   Expected: new release uses the new path.
3. Verify the import that failed now works.

## When this applies
Use this when code does `from statsmodels.compat.pandas import Appender` on a recent statsmodels.

## When it does not apply
If the error names a different statsmodels.compat member, check whether the shim still exists. If statsmodels itself will not import, reinstall it.

## Compatibility
Recent statsmodels versions where the compat shim was removed. pandas.util._decorators.Appender exists across pandas 1.x and 2.x.

## Root cause
statsmodels.compat.pandas held shims for pandas API drift, including a re-export of pandas' Appender docstring decorator. statsmodels cleaned the module up and dropped the re-export; anything importing it breaks.

## Edge cases
Appender is itself semi-private in pandas (pandas.util._decorators), so prefer upgrading the dependent package over relying on the new path long-term. Grep for other statsmodels.compat imports when upgrading.