def get_session_token(self):
        ''' get session token '''
        # HTTP POST query to session authenticate API
        try:
            response = requests.post(self.__session_url__ + 'sessionauth/v1/authenticate',
                                     cert=(self.__crt__, self.__key__), verify=True)
        except requests.exceptions.RequestException as err:
            self.logger.error(err)
            raise
        if response.status_code == 200:
            # load json response as list
            data = json.loads(response.text)
            self.logger.debug(data)
            # grab token from list
            session_token = data['token']
        else:
            raise Exception('BAD HTTP STATUS: %s' % str(response.status_code))
        # return the token
        self.logger.debug(session_token)
        return session_token
get session token