code: func getMetric(store *cassandra.CassandraStore, amkey schema.AMKey) ([]Metric, error) {
  	var metrics []Metric
  	// index only stores MKey's, not AMKey's.
  	iter := store.Session.Query("select name from metric_idx where id=? ALLOW FILTERING", amkey.MKey.String()).Iter()
  	var m Metric
  	for iter.Scan(&m.name) {
  		m.AMKey = amkey
  		metrics = append(metrics, m)
  	}
  	if len(metrics) > 1 {
  		panic(fmt.Sprintf("wtf. found more than one entry for id %s: %v", amkey.String(), metrics))
  	}
  	err := iter.Close()
  	if err != nil {
  		return metrics, err
  	}
  	return metrics, nil
  }
docs: // getMetric returns the metric for the given AMKey