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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 get(self, url):
        '''Get the entity that corresponds to URL.'''
        robots_url = Robots.robots_url(url)
        if robots_url not in self.cache:
            self.cache[robots_url] = ExpiringObject(partial(self.factory, robots_url))
        return self.cache[robots_url].get()