<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def register_model(self, model):
 """ Register ``model`` to this group :param model: model name :return: None """


        assert isinstance(model, str)
        if model not in self.all_models:
            self.all_models.append(model)