8.4.0
* New itertools
* :func:`mark_ends`
* :func:`is_sorted`
* Changes to existing itertools:
* :func:`islice_extended` can now be used with real slices
* The implementations for :func:`filter_except` and :func:`map_except` were improved
* Other changes
* Automated tests now enforce code style (using `black <https://github.com/psf/black>`__)
* The various signatures of :func:`islice_extended` and :func:`numeric_range` now appear in the docs
* The test configuration for mypy was updated
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