def pending_feature(not_yet_implemented):
    """
    Indicate that a callable's implementation is not complete or not stable.
    
    This simplifies designation and application of this concept, 
    and it simplifies removal once the implementation is ready for use.
    
    :param callable not_yet_implemented: the function or class not ready to be
        used, i.e. that's pending implementation.
    :return callable: object that will raise NotImplementedError if called.
    """
    def raise_error(*args, **kwargs):
        raise NotImplementedError("{} is not fully implemented".
                                  format(not_yet_implemented.__name__))
    return raise_error