>>> Cluster(0, 0, 0, 0, 0, 0, 0, 0).timeline
        0
        >>> Cluster(0, 0, 0, 0, 0, 0, 0, TimelineHistory.from_node(1, '[]')).timeline
        1
        >>> Cluster(0, 0, 0, 0, 0, 0, 0, TimelineHistory.from_node(1, '[["a"]]')).timeline
        0

def timeline(self):
        """
        >>> Cluster(0, 0, 0, 0, 0, 0, 0, 0).timeline
        0
        >>> Cluster(0, 0, 0, 0, 0, 0, 0, TimelineHistory.from_node(1, '[]')).timeline
        1
        >>> Cluster(0, 0, 0, 0, 0, 0, 0, TimelineHistory.from_node(1, '[["a"]]')).timeline
        0
        """
        if self.history:
            if self.history.lines:
                try:
                    return int(self.history.lines[-1][0]) + 1
                except Exception:
                    logger.error('Failed to parse cluster history from DCS: %s', self.history.lines)
            elif self.history.value == '[]':
                return 1
        return 0