docs: def _hdfs_namenode_metrics(self, beans, metrics, tags):
          """
          Get HDFS namenode metrics from JMX
          """
          bean = next(iter(beans))
          bean_name = bean.get('name')
  
          if bean_name != bean_name:
              raise Exception("Unexpected bean name {}".format(bean_name))
  
          for metric, (metric_name, metric_type) in iteritems(metrics):
              metric_value = bean.get(metric)
  
              if metric_value is not None:
                  self._set_metric(metric_name, metric_type, metric_value, tags)
  
          if 'CapacityUsed' in bean and 'CapacityTotal' in bean:
              self._set_metric(
                  'hdfs.namenode.capacity_in_use',
                  self.GAUGE,
                  float(bean['CapacityUsed']) / float(bean['CapacityTotal']),
                  tags,
              )