        def register(*types):
            """
            Decorator to register an implementation for the given types
            """
            check(types)

            def dec(f):
                check(getfullargspec(f).args, operator.lt, ' in ' + f.__name__)
                typemap[types] = f
                return f

            return dec
Decorator to register an implementation for the given types
prometheus_client/decorator.py