You're looking at StableBuild's Deleted PyPI mirror - where we index all deleted packages from the Python package registry.

arsein
7.6.1b0

This version was deleted from PyPI around 2024-02-02. Installing fails with:
$ pip3 install arsein==7.6.1b0 ERROR: Could not find a version that satisfies the requirement arsein==7.6.1b0
View other deleted versions of arsein

Install through StableBuild

You can install this package from StableBuild's PyPI snapshots from before the version was deleted:
pip3 install \ -i https://YOUR_API_KEY.pypimirror.stablebuild.com/2024-02-01/ \ arsein==7.6.1b0
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Or, download files manually

And install manually via pip:
Arsein-7.6.1b0-py3-none-any.whl (22.0KB)
Arsein-7.6.1b0.tar.gz (20.4KB)