Worked on enhancing type hinting for the pandas-dev/pandas-stubs repository, focusing on improving the static typing of the frame.join method to support cross join semantics. Updated the typing stubs by replacing the deprecated JoinHow with MergeHow and incorporated the 'cross' join option, ensuring type hints accurately reflect current pandas functionality. Developed new tests in Python to validate type checking for various join methods, including cross joins, thereby increasing test coverage and reliability. Employed skills in Python, testing, and type hinting to deliver a feature that improves type checker accuracy and the overall developer experience when using pandas-stubs.