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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def register_model(self, model_cls):
 """Decorator for registering model."""

        if not getattr(model_cls, '_database_'):
            raise ModelAttributeError('_database_ missing '
                                      'on %s!' % model_cls.__name__)
        if not getattr(model_cls, '_collection_'):
            raise ModelAttributeError('_collection_ missing '
                                      'on %s!' % model_cls.__name__)

        model_cls._mongo_client_ = self.client

        logging.info('Registering Model ' + model_cls.__name__)
        return model_cls