def load(self, filename, create_if_missing=True):
        filename = Path(filename)
        if not filename.exists() and create_if_missing:
            self.load_pip_requirements()
            with filename.open("w") as f:
                f.write(yaml.dump(self.serialized, default_flow_style=False,
                                  encoding=None))
            self.filename = filename
            return self.save(filename)
        with filename.open() as f:
            for group, requirements in yaml.load(f.read()).items():
                for requirement in requirements:
                    self[group].add(Requirement.coerce(requirement))
        self.filename = filename
def test_populate_old_value_of_change_with_invalid_state(self):
        self.save_new_default_exploration('exp1', self.author_id)
        expected_suggestion_dict = self.suggestion_dict
        suggestion = suggestion_registry.SuggestionEditStateContent(
            expected_suggestion_dict['suggestion_id'],
            expected_suggestion_dict['target_id'],
            expected_suggestion_dict['target_version_at_submission'],
            expected_suggestion_dict['status'], self.author_id,
            self.reviewer_id, expected_suggestion_dict['change'],
            expected_suggestion_dict['score_category'],
            expected_suggestion_dict['language_code'], False, self.fake_date)

        suggestion.change.state_name = 'invalid_state_name'

        self.assertIsNone(suggestion.change.old_value)

        suggestion.populate_old_value_of_change()

        self.assertIsNone(suggestion.change.old_value)