def add(self, elem, replace=False):
        """Add a requirement.

        :param elem: a string or :class:`Requirement` instance.
        :param replace: if `True`, packages in the set with the same name will
            be removed first.
        """
        if isinstance(elem, text_type):
            elem = Requirement.coerce(elem)
        if replace and elem in self:
            self.remove(elem)
        super(Requirements, self).add(elem)
def test_contructor_raise_exception_for_invalid_state_shema_version(self):
        score_category = (
            suggestion_models.SCORE_TYPE_QUESTION +
            suggestion_models.SCORE_CATEGORY_DELIMITER + 'skill_id')
        change = {
            'cmd': (
                question_domain
                .CMD_CREATE_NEW_FULLY_SPECIFIED_QUESTION),
            'question_dict': {
                'question_state_data': self.VERSION_27_STATE_DICT,
                'question_state_data_schema_version': 23,
                'language_code': 'en',
                'linked_skill_ids': ['skill_id'],
                'inapplicable_skill_misconception_ids': []
            },
            'skill_id': 'skill_id',
            'skill_difficulty': 0.3
        }
        self.assertEqual(
            change['question_dict']['question_state_data_schema_version'], 23)

        with self.assertRaisesRegex(
            utils.ValidationError,
            'Expected state schema version to be in between 25'
        ):
            suggestion_registry.SuggestionAddQuestion(
                'suggestionId', 'target_id', 1,
                suggestion_models.STATUS_IN_REVIEW, self.author_id, None,
                change, score_category, 'en', False, self.fake_date)