def build_getter(validator, getter_namespace=None):
    """Create a getter function for retrieving values from the config cache.
    Getters will default to the DEFAULT namespace.
    """
    def proxy_register(key_name, default=UndefToken, help=None, namespace=None):
        name        = namespace or getter_namespace or config.DEFAULT
        namespace   = config.get_namespace(name)
        return proxy_factory.build(validator, namespace, key_name, default, help)

    return proxy_register