code: func (b *EtcdBackend) DeleteRange(ctx context.Context, startKey, endKey []byte) error {
  	if len(startKey) == 0 {
  		return trace.BadParameter("missing parameter startKey")
  	}
  	if len(endKey) == 0 {
  		return trace.BadParameter("missing parameter endKey")
  	}
  	start := b.clock.Now()
  	_, err := b.client.Delete(ctx, prependPrefix(startKey), clientv3.WithRange(prependPrefix(endKey)))
  	writeLatencies.Observe(time.Since(start).Seconds())
  	writeRequests.Inc()
  	if err != nil {
  		return trace.Wrap(convertErr(err))
  	}
  	return nil
  }
docs: // DeleteRange deletes range of items with keys between startKey and endKey