def encode_pair(f):
    # Decorator function to encode "pair" to bytes object
    def new_f(*args, **kwargs):
        args = list(args)
        pair = args[1]
        if type(pair) == str:
            args[1] = pair.encode()
        assert type(args[1]) == bytes
        args = tuple(args)
        return f(*args, **kwargs)
    return new_f