code: def add_answer_for_student(student_item, vote, rationale):
      
      answers = get_answers_for_student(student_item)
      answers.add_answer(vote, rationale)
  
      sub_api.create_submission(student_item, {
          ANSWER_LIST_KEY: answers.get_answers_as_list()
      })
docs: 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