code: func EnsureRackKVMs(c context.Context, cfgs []*config.Datacenter, kvmIds map[string]int64) error {
  	t := &RackKVMsTable{}
  	t.kvms = kvmIds
  	if err := t.fetch(c); err != nil {
  		return errors.Annotate(err, "failed to fetch racks").Err()
  	}
  	if err := t.computeChanges(c, cfgs); err != nil {
  		return errors.Annotate(err, "failed to compute changes").Err()
  	}
  	if err := t.update(c); err != nil {
  		return errors.Annotate(err, "failed to update racks").Err()
  	}
  	return nil
  }
docs: // EnsureRackKVMs ensures the database contains exactly the given rack kvm_ids.