def register_vcs_handler(vcs: str, method: str) -> Callable:  # decorator
    """Create decorator to mark a method as the handler of a VCS."""

    def decorate(f: Callable) -> Callable:
        """Store f in HANDLERS[vcs][method]."""
        HANDLERS.setdefault(vcs, {})[method] = f
        return f

    return decorate
Create decorator to mark a method as the handler of a VCS.
versioneer.py