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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 save(self):
 """Pickle the addressbook and a timestamp """

        if self.contacts:  # never write a empty addressbook
            cache = {'contacts': self.contacts,
                     'aadbook_cache': CACHE_FORMAT_VERSION}
            pickle.dump(cache, open(self._config.cache_filename, 'wb'))