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

mstk
0.3.20

This version was deleted from PyPI around 2024-12-05. Installing fails with:
$ pip3 install mstk==0.3.20 ERROR: Could not find a version that satisfies the requirement mstk==0.3.20
View other deleted versions of mstk

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/2024-12-04/ \ mstk==0.3.20
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Or, download files manually

And install manually via pip:
mstk-0.3.20-py3-none-any.whl (279.5KB)
mstk-0.3.20.tar.gz (235.2KB)