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

shared-atomic-enterprise
4!2.3.5

This version was deleted from PyPI around 2025-03-22. Installing fails with:
$ pip3 install shared-atomic-enterprise==4!2.3.5 ERROR: Could not find a version that satisfies the requirement shared-atomic-enterprise==4!2.3.5