def all(self):
        """
        Returns a list of cached instances.
        """
        class_list = list(self.get_class_list())
        if not class_list:
            self.cache = []
            return []

        if self.cache is not None:
            return self.cache

        results = []
        for cls_path in class_list:
            module_name, class_name = cls_path.rsplit('.', 1)
            try:
                module = __import__(module_name, {}, {}, class_name)
                cls = getattr(module, class_name)
                if self.instances:
                    results.append(cls())
                else:
                    results.append(cls)
            except Exception:
                logger.exception('Unable to import {cls}'.format(cls=cls_path))
                continue
        self.cache = results

        return results
Returns a list of cached instances.