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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 _decrypt(self, rj, token):
 """ Decrypt an encrypted JsonWebToken :param rj: :py:class:`cryptojwt.jwe.JWE` instance :param token: The encrypted JsonWebToken :return: """

        if self.iss:
            keys = self.key_jar.get_jwt_decrypt_keys(rj.jwt, aud=self.iss)
        else:
            keys = self.key_jar.get_jwt_decrypt_keys(rj.jwt)
        return rj.decrypt(token, keys=keys)