Developed a new C++ interface for set operations on labeled data within the metatensor/metatensor repository, focusing on the Labels::set_difference functionality. The implementation introduced an optional mapping feature to track the positions of input elements in the resulting set difference, supporting more precise differential analysis on labeled datasets. Emphasizing API consistency and maintainability, the work aligned with existing Labels operations to ensure a cohesive developer experience. Leveraging expertise in C++ development, API design, and software engineering, the contribution enhanced data processing workflows and enabled improved traceability for downstream analytics, addressing a specific need for trackable set-difference operations in scientific computing.