Narwhals v1.19.0

Changes

🚀 Performance improvements

• perf: streamline pyarrow and pandas group by agg (#1621)

✨ Enhancements

• feat: add Series|Expr.rolling_var and Series|Expr.rolling_std (#1451)
• fix: Add support for pandas cumulative operations with over (#1565)
• feat: add var to Expr and Series (#1603)

🐞 Bug fixes

• fix: nw.col('a').is_in(df['b']) was raising (#1616)
• fix: pandas and pyarrow were raising for repeated aggregations involving the same root name and the same aggregation function (#1613)

📖 Documentation

• docs: more args and returns documentation in DataFrame class (#1600)
• docs: make docstring examples function names more descriptive in functions.py (#1602)
• docs: improve DataFrame, LazyFrame and Series docstrings (#1622)

🛠️ Other improvements

• ci: unpin scikit-learn in scikit-lego test (#1611)
• ci: Speed up tests in local development (#1608)
• test: downstream test for tea-tasting (#1605)
• test: minimum versions (#1617)

Thank you to all our contributors for making this release possible!
@ClaudioSalvatoreArcidiacono, @DeaMariaLeon, @Dhanunjaya-Elluri, @FBruzzesi, @Machele-codez, @MarcoGorelli, @e10v, @marenwestermann and @skritsotalakis