code: def submit_response(self, assessment_section_id, item_id, answer_form):
          
          if not isinstance(answer_form, ABCAnswerForm):
              raise errors.InvalidArgument('argument type is not an AnswerForm')
  
          # OK, so the following should actually NEVER be true. Remove it?
          if answer_form.is_for_update():
              raise errors.InvalidArgument('the AnswerForm is for update only, not submit')
          #
  
          try:
              if self._forms[answer_form.get_id().get_identifier()] == SUBMITTED:
                  raise errors.IllegalState('answer_form already used in a submit transaction')
          except KeyError:
              raise errors.Unsupported('answer_form did not originate from this assessment session')
          if not answer_form.is_valid():
              raise errors.InvalidArgument('one or more of the form elements is invalid')
          answer_form._my_map['_id'] = ObjectId()
          self.get_assessment_section(assessment_section_id).submit_response(item_id, answer_form)
          self._forms[answer_form.get_id().get_identifier()] = SUBMITTED
docs: Submits an answer to an item.
  
          arg:    assessment_section_id (osid.id.Id): ``Id`` of the
                  ``AssessmentSection``
          arg:    item_id (osid.id.Id): ``Id`` of the ``Item``
          arg:    answer_form (osid.assessment.AnswerForm): the response
          raise:  IllegalState - ``has_assessment_section_begun()`` is
                  ``false or is_assessment_section_over()`` is ``true``
          raise:  InvalidArgument - one or more of the elements in the
                  form is invalid
          raise:  NotFound - ``assessment_section_id`` or ``item_id`` is
                  not found, or ``item_id`` not part of
                  ``assessment_section_id``
          raise:  NullArgument - ``assessment_section_id, item_id,`` or
                  ``answer_form`` is ``null``
          raise:  OperationFailed - unable to complete request
          raise:  PermissionDenied - authorization failure
          raise:  Unsupported - ``answer_form`` is not of this service
          *compliance: mandatory -- This method must be implemented.*