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

vpp-papi.stable
20.1

This version was deleted from PyPI around 2024-09-12. Installing fails with:
$ pip3 install vpp-papi.stable==20.1 ERROR: Could not find a version that satisfies the requirement vpp-papi.stable==20.1

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/2024-09-11/ \ vpp-papi.stable==20.1
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Or, download files manually

And install manually via pip: