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

sagemath-objects
10.5rc1

This version was deleted from PyPI around 2025-02-12. Installing fails with:
$ pip3 install sagemath-objects==10.5rc1 ERROR: Could not find a version that satisfies the requirement sagemath-objects==10.5rc1

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/2025-02-11/ \ sagemath-objects==10.5rc1
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Or, download files manually

And install manually via pip: