def prepare_schemes(self, req):

        # fix test bug when in python3 scheme, more details in commint msg
        ret = sorted(self.__schemes__ & set(req.schemes), reverse=True)

        if len(ret) == 0:
            raise ValueError('No schemes available: {0}'.format(req.schemes))
        return ret
make sure this client support schemes required by current request
dataset/ETHPy150Open mission-liao/pyswagger/pyswagger/core.py/BaseClient.prepare_schemes