## Checklist

- [ ] I have read the [OpenWISP Contributing Guidelines](http://openwisp.io/docs/developer/contributing.html).
- [ ] I have manually tested the changes proposed in this pull request.
- [ ] I have written new test cases for new code and/or updated existing tests for changes to existing code.
- [ ] I have updated the documentation.

## Reference to Existing Issue

Closes #<issue-number>.

Please [open a new issue](https://github.com/openwisp/django-swappable-models/issues/new/choose) if there isn't an existing issue yet.

## Description of Changes

Please describe these changes.

## Screenshot

Please include any relevant screenshots.
