Jerry Jinfeng Guo developed the foundational structure for the PowerGridModel/power-grid-model repository, focusing on reliability and maintainability from the outset. He established the initial project skeleton and branching strategy in C++, then addressed error handling by refining transformer error messages to use deduplicated and sorted unique IDs. To ensure robustness, Jerry expanded unit testing to cover complex transformer scenarios, including three-winding transformers with multiple edges, thereby reducing the risk of regressions. His work combined C++ development with a strong emphasis on error handling and unit testing, resulting in a solid base for future feature delivery and improved code quality.