Worked on the NHSDigital/manage-vaccinations-in-schools-testing repository, focusing on backend development and type hinting using Python. Delivered targeted improvements to type safety and code readability in the Import and Login modules, specifically updating the year_groups parameter in pg_import_records.py from an optional integer to an optional list of integers and removing a strict return type annotation in pg_login.py to allow greater flexibility. These changes enhanced compile-time checks and prepared the codebase for easier maintenance and faster future feature delivery. The work prioritized preventive quality enhancements, supporting more reliable downstream integrations and improving the overall developer experience for future contributors.