def _traverse(self, n=1):
        if not self.history:
            raise exceptions.RoboError('Not tracking history')
        cursor = self._cursor + n
        if cursor >= len(self._states) or cursor < 0:
            raise exceptions.RoboError('Index out of range')
        self._cursor = cursor
Tuple of ordered fields for this :class:`ColumnTS`.
dataset/ETHPy150Open jmcarp/robobrowser/robobrowser/browser.py/RoboBrowser._traverse--crossover with--dataset/ETHPy150Open lsbardel/python-stdnet/stdnet/apps/columnts/models.py/ColumnTS.fields