docs: def add_attempts(self, attempts):
          """stub"""
          if attempts is None:
              raise NullArgument('attempts cannot be None')
          if not self.my_osid_object_form._is_valid_integer(
                  attempts, self.get_attempts_metadata()):
              raise InvalidArgument('attempts')
          self.my_osid_object_form._my_map['attempts'] = attempts