Return an instance of the model_class from the cache if it is present.

        Args:
            model_class (:class:`cinder_data.model.CinderModel`): A subclass of
                :class:`cinder_data.model.CinderModel` of your chosen model.
            record_id (int): The id of the record requested.

        Returns:
            :class:`cinder_data.model.CinderModel`: An instance of model_class or None.

def peek_record(self, model_class, record_id):
        """Return an instance of the model_class from the cache if it is present.

        Args:
            model_class (:class:`cinder_data.model.CinderModel`): A subclass of
                :class:`cinder_data.model.CinderModel` of your chosen model.
            record_id (int): The id of the record requested.

        Returns:
            :class:`cinder_data.model.CinderModel`: An instance of model_class or None.
        """
        if self._cache:
            return self._cache.get_record(model_class.__name__, record_id)
        else:
            return None