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

mentpy
0.1.0a3

This version was deleted from PyPI around 2023-10-24. Installing fails with:
$ pip3 install mentpy==0.1.0a3 ERROR: Could not find a version that satisfies the requirement mentpy==0.1.0a3
View other deleted versions of mentpy

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/2023-10-23/ \ mentpy==0.1.0a3
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Or, download files manually

And install manually via pip:
mentpy-0.1.0a3-py3-none-any.whl (61.2KB)
mentpy-0.1.0a3.tar.gz (49.5KB)