def answer_yn(question=None):
    """Prints a simple yes or no question and returns bool"""
    while True:
        answer = input(question or 'Are you sure? Y/n').lower()
        if answer == '' or answer == 'y' or answer == 'yes':
            return True
        elif answer == 'n' or answer == 'no':
            return False

        print('Please enter a valid answer (Y/n)')