def yes_no(question):





    while True:
        response = input(question).lower()

        # check if user says yes or no
        if response == "yes" or response == 'y':
            return "yes"
        elif response == "no" or response == 'n':
            return 'no'
        else:
            print('please enter yes / no')
           

# Main routine

# testing loop...
while True:
    instructions = yes_no('Do you want to see the instructions? ')
    print(f'you choose {instructions}')