Narwhals v1.1.1

Changes

✨ Enhancements

• feat: allow nw.len in groupby for arrow (#540)
• feat: add len to pyarrow series and expr (#538)
• feat: ArrowExprCatNamespace (#536)
• feat: add is_null and __invert__ to pyarrow series (#534)
• enh: ruff S rule fix (#526)
• feat: implement Series.sum for pyarrow (#495)
• feat: pyarrow concat (#525)
• feat: pyarrow lit (#524)

📖 Documentation

• ci: fix exception in code snippet, add check to CI (#532)

🛠️ Other improvements

• ci: actually use pandas nightly in pandas-nightly build (#539)
• ci: remove [dev] from sklego install (#535)
• chore: ruff rules (#527)
• ci: add downstream tests for altair + scikit-lego (#533)
• ci: fix exception in code snippet, add check to CI (#532)
• test: conftest constructors refactoring (#515)

Thank you to all our contributors for making this release possible!
@FBruzzesi, @MarcoGorelli, @anopsy, @lucianosrp and @mfonekpo