def add_answer_for_student(student_item, vote, rationale):
answers = get_answers_for_student(student_item)<EOL>answers.add_answer(vote, rationale)<EOL>sub_api.create_submission(student_item, {<EOL>ANSWER_LIST_KEY: answers.get_answers_as_list()<EOL>})<EOL>
Add an answer for a student to the backend

Args:
    student_item (dict): The location of the problem this submission is
        associated with, as defined by a course, student, and item.
    vote (int): the option that student voted for
    rationale (str): the reason why the student vote for the option