More-itertools

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* New functions
* :func:`iter_index` (from the Python itertools docs)
* :func:`transpose` (from the Python itertools docs)
* :func:`matmul` (from the Python itertools docs)
* :func:`factor` (from the Python itertools docs)
* :func:`gray_product` (thanks to haukex)
* :func:`partial_product` (thanks to lonnen)

* Changes to existing functions
* :func:`sieve` was updated to match the Python itertools docs
* :func:`maxsplit` was updated to fix a bug (thanks to abingham)
* :func:`sliced` had its `type hint <https://github.com/more-itertools/more-itertools/pull/667>`__ updated (thanks to ad-chaos)


* Other changes
* The ``batched`` function is marked as deprecated and will be removed in a future major release. For Python 3.12 and above, use ``itertools.batched`` instead. (thanks to neutrinoceros)
* The type hints now used postponed evaluation of annotations from PEP 563 (thanks to Isira-Seneviratne)
* Some documentation issues were fixed (thanks to Voskov and jdkandersson)

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* Potentially breaking changes
* :func:`grouper` no longer accepts an integer as its first argument. Previously this raised a ``DeprecationWarning``.
* :func:`collate` has been removed. Use the built-in :func:`heapq.merge` instead.
* :func:`windowed` now yields nothing when its iterable is empty.
* This library now advertises support for Python 3.7+.

* New functions
* :func:`constrained_batches`
* :func:`batched` (from the Python itertools docs)
* :func:`polynomial_from_roots` (from the Python itertools docs)
* :func:`sieve` (from the Python itertools docs)

* Other changes
* Some documentation issues were fixed (thanks to nanouasyn)

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* New functions
* :func:`longest_common_prefix` (thanks to nanouasyn)
* :func:`iequals` (thanks to nanouasyn)

* Changes to existing functions
* `concurrent.futures.ThreadPoolExecutor` is now imported lazily in :func:`callback_iter`.
* :func:`tail` is now optimized for iterables with a fixed length.

* Other changes
* Some documentation issues were fixed (thanks to pochmann and timgates42)
* This library is now marked for Python 3.10 compatibility in PyPI (thanks to chayim)

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* New functions
* The :func:`subslices` recipe from the `itertools` docs was added (thanks to rhettinger)

* Changes to existing functions
* The :func:`ichunked` function is now more efficient (thanks to hjtran0 and seanmacavaney)
* The :func:`difference` function is now more efficient (thanks to Masynchin)
* The :func:`grouper` recipe now has more features, mirroring the one in the `itertools` docs (thanks to rhettinger)

* Other changes
* Some documentation issues were fixed (thanks to medvied and Freed-Wu)
* The `more_itertools` package is now built with `flit` (thanks to mgorny)

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* Bug fixes
* Some documentation issues were fixed (thanks to Masynchin, spookylukey, astrojuanlu, and stephengmatthews)
* Python 3.5 support was temporarily restored (thanks to mattbonnell)

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* New functions
* The :func:`before_and_after`, :func:`sliding_window`, and :func:`triplewise` recipes from the Python 3.10 docs were added
* :func:`duplicates_everseen` and :func:`duplicates_justseen` (thanks to OrBin and DavidPratt512)
* :func:`minmax` (thanks to Ricocotam, MSeifert04, and ruancomelli)
* :func:`strictly_n` (thanks to hwalinga and NotWearingPants)
* :func:`unique_in_window`

* Changes to existing functions
* :func:`groupby_transform` had its type stub improved (thanks to mjk4 and ruancomelli)
* :func:`is_sorted` now accepts a ``strict`` parameter (thanks to Dutcho and ruancomelli)
* :func:`zip_broadcast` was updated to fix a bug (thanks to kalekundert)