def yes_or_no(question):
    """ a utility tool to ask the user yes/no question

    Parameters
    ----------
    question : str
        the text for the question

    Returns
    -------
    value : bool
        True or False

    """
    while True:
        answer = input(question + ' (y/n): ').lower().strip()
        if answer in ('y', 'yes', 'n', 'no'):
            return answer in ('y', 'yes')
        else:
            print('You must answer y, yes, n, or no.')