docs: def answer(request):
      """
      Save the answer.
  
      GET parameters:
          html:
              turn on the HTML version of the API
  
      BODY
      json in following format:
      {
          "answer": #answer,                          -- for one answer
          "answers": [#answer, #answer, #answer ...]  -- for multiple answers
      }
  
      answer = {
          "answer_class": str,            -- class of answer to save (e.g., flashcard_answer)
          "response_time": int,           -- response time in milliseconds
          "meta": "str"                   -- optional information
          "time_gap": int                 -- waiting time in frontend in seconds
          ...                             -- other fields depending on aswer type
                                            (see from_json method of Django model class)
      }
      """
      if request.method == 'GET':
          return render(request, 'models_answer.html', {}, help_text=answer.__doc__)
      elif request.method == 'POST':
          practice_filter = get_filter(request)
          practice_context = PracticeContext.objects.from_content(practice_filter)
          saved_answers = _save_answers(request, practice_context, True)
          return render_json(request, saved_answers, status=200, template='models_answer.html')
      else:
          return HttpResponseBadRequest("method %s is not allowed".format(request.method))