def check_verifier(self, verifier):
        """Checks that the verifier contains only safe characters
        and is no shorter than lower and no longer than upper.
        """
        lower, upper = self.verifier_length
        return (set(verifier) <= self.safe_characters and
                len(verifier) <= upper <= lower)
dataset/ETHPy150Open hzlf/openbroadcast/services/bcmon/requests/packages/oauthlib/oauth1/rfc5849/__init__.py/Server.check_verifier/swapped operands of `<=`