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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 __filename(self, id):
 """Return the cache file name for an entry with a given id."""

        suffix = self.fnsuffix()
        filename = "%s-%s.%s" % (self.fnprefix, id, suffix)
        return os.path.join(self.location, filename)