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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 __instances(self):
 """ Cache instances, allowing generators to be used and reused. This fills a cache as the generator gets emptied, eventually reading exclusively from the cache. """

        for instance in self.__instances_cache:
            yield instance
        for instance in self.__instances_original:
            self.__instances_cache.append(instance)
            yield instance