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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 CELERY_RESULT_BACKEND(self):
 """Redis result backend config"""


        # allow specify directly
        configured = get('CELERY_RESULT_BACKEND', None)
        if configured:
            return configured

        if not self._redis_available():
            return None

        host, port = self.REDIS_HOST, self.REDIS_PORT

        if host and port:
            default = "redis://{host}:{port}/{db}".format(
                    host=host, port=port,
                    db=self.CELERY_REDIS_RESULT_DB)

        return default