The latter (although some are original works); if you browse https://stablelib.com/v1/ https://stablelib.com/v1/, you can see links to upstreams for each packag

The latter (although some are original works); if you browse https://stablelib.com/v1/ https://stablelib.com/v1/, you can see links to upstreams for each package in "Information" section. Improvements are sent via whatever method the original accepts, mostly GitHub pull requests.