def register_vcs_handler(vcs, method):  # decorator
    """Create decorator to mark a method as the handler of a VCS."""
    def decorate(f):
        """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