Worked on the goldmansachs/legend-engine repository to enhance GraphQL SDL generation by enabling correct handling of abstract types. This improvement addressed schema-generation errors by ensuring that abstract types are properly recognized and processed during schema creation. The approach involved code refactoring in Java, focusing on schema generation logic and incorporating comprehensive testing to validate the new functionality. By adding targeted tests, the work aimed to prevent regressions and maintain accuracy in future updates. The changes contributed to more reliable schema outputs and streamlined the development process for projects relying on GraphQL. Skills applied included Java, GraphQL, abstract types, and testing.