Felix Berkhahn developed a sub-package installation capability for multi-package Python projects within the hawk-ai-aml/github-actions repository. He enhanced the GitHub Actions CI workflow by introducing a new input, subPackagesDirs, allowing users to specify sub-packages for installation. Using YAML to define workflow steps, Felix automated the creation of a virtual environment and the installation of sub-packages with development dependencies, streamlining testing and build processes across multiple packages. His work leveraged CI/CD best practices and Python packaging expertise to reduce manual configuration, enabling scalable, end-to-end testing for complex repositories and improving onboarding efficiency for new Python packages.