Polars: py-0.20.9 Release

🚀 Performance improvements

• use owned arithmetic in horizontal_sum (#14525)

✨ Enhancements

• Add writable flag to DataFrame.to_numpy (#14520)
• flatten aliases (#14512)
• Make formatting more consistent in DOT graphs (#14486)
• add flush operator to streaming operators (#14500)

🐞 Bug fixes

• ensure the streaming dispatcher can replace placeholders in unions (#14537)
• Ensure series are contiguous prior to transpose (#14527)
• write csv header if necessary when finishing sinks (#14518)
• fix logical dtypes in take_chunked (#14517)
• fix binary-offset row-encode (#14514)
• race conditions in OOC writing (#14510)
• Remove is_numeric check on Series.std/var (#14493)
• Error on invalid schema input in DataFrame constructor (#14483)

📖 Documentation

• Fix docstring example for Config.save_to_file (#14533)
• Fix infer_schema_length param description (#14233)
• Clean up grammar and capitalization in README.md (#14488)
• Add examples for Series.bin.ends_with, Series.bin.starts_with, Series.bin.decode, Series.bin.encode. (#14478)

🛠️ Other improvements

• add code coverage CI (#14532)
• Re-enable streaming OOC tests (#14522)
• Use constant for checking Sphinx building (#14502)

Thank you to all our contributors for making this release possible! @FBruzzesi, @NedJWestern, @c-peters, @dannyfriar, @i-aki-y, @jdanford, @mbuhidar, @mcrumiller, @ritchie46, @stinodego and @taki-mekhalfa