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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 _create_cache_filename(self, source_file):
 """ return the cache file name for a header file. :param source_file: Header file name :type source_file: str :rtype: str """

        res = self._create_cache_key(source_file) + ".cache"
        return os.path.join(self.__dir, res)