Wencheng Yao developed a new User Defined Function called split_part for the Reasoner module in the OpenSPG/openspg repository, enabling string splitting by a separator with support for negative indices to retrieve elements from the end of the split array. He approached the task with a focus on backend and Java development, implementing comprehensive unit tests to cover a wide range of inputs and edge cases. By aligning the feature with project requirements, Wencheng enhanced the flexibility of data extraction in query expressions. His work demonstrated careful attention to test-driven development and code quality, resulting in a robust and maintainable solution.