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

opencv-python-headless
3.4.10.35

This version was deleted from PyPI around 2024-06-03. Installing fails with:
$ pip3 install opencv-python-headless==3.4.10.35 ERROR: Could not find a version that satisfies the requirement opencv-python-headless==3.4.10.35

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/2024-06-02/ \ opencv-python-headless==3.4.10.35
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