code: def _get_or_create_student_item(student_item_dict):
      
      try:
          try:
              return StudentItem.objects.get(**student_item_dict)
          except StudentItem.DoesNotExist:
              student_item_serializer = StudentItemSerializer(
                  data=student_item_dict
              )
              if not student_item_serializer.is_valid():
                  logger.error(
                      u"Invalid StudentItemSerializer: errors:{} data:{}".format(
                          student_item_serializer.errors,
                          student_item_dict
                      )
                  )
                  raise SubmissionRequestError(field_errors=student_item_serializer.errors)
              return student_item_serializer.save()
      except DatabaseError:
          error_message = u"An error occurred creating student item: {}".format(
              student_item_dict
          )
          logger.exception(error_message)
          raise SubmissionInternalError(error_message)
docs: Gets or creates a Student Item that matches the values specified.
  
      Attempts to get the specified Student Item. If it does not exist, the
      specified parameters are validated, and a new Student Item is created.
  
      Args:
          student_item_dict (dict): The dict containing the student_id, item_id,
              course_id, and item_type that uniquely defines a student item.
  
      Returns:
          StudentItem: The student item that was retrieved or created.
  
      Raises:
          SubmissionInternalError: Thrown if there was an internal error while
              attempting to create or retrieve the specified student item.
          SubmissionRequestError: Thrown if the given student item parameters fail
              validation.
  
      Examples:
          >>> student_item_dict = dict(
          >>>    student_id="Tim",
          >>>    item_id="item_1",
          >>>    course_id="course_1",
          >>>    item_type="type_one"
          >>> )
          >>> _get_or_create_student_item(student_item_dict)
          {'item_id': 'item_1', 'item_type': 'type_one', 'course_id': 'course_1', 'student_id': 'Tim'}