fetch the chart identified by this chart's next_id attribute
        if the next_id is either null or not present for this chart return None
        returns the new chart instance on sucess

def next(self):
        """
        fetch the chart identified by this chart's next_id attribute
        if the next_id is either null or not present for this chart return None
        returns the new chart instance on sucess"""
        try:
            if self.next_id:
                return Chart(self.next_id)
            else:
                log.debug('attempted to get next chart, but none was found')
                return
        except AttributeError:
            #chart does not implement next pointer
            log.debug('attempted to get next chart from a chart without a next attribute')
            return None