Denis Mazur developed a flexible PyTorch version selection mechanism for local builds in the pytorch/tensordict repository. By enabling the use of the PYTORCH_VERSION environment variable within setup.py, Denis activated previously dormant local-build logic to allow developers to specify PyTorch versions during setup. This approach, implemented in Python and leveraging environment variable management and build system configuration, improved build reproducibility and streamlined the onboarding process for new contributors. The work addressed version-related troubleshooting by making local development more predictable. Over the course of the month, Denis focused on this targeted feature, demonstrating depth in Python scripting and configuration management.