code: func EnsureVLANs(c context.Context, cfgs []*config.VLAN) error {
  	t := &VLANsTable{}
  	if err := t.fetch(c); err != nil {
  		return errors.Annotate(err, "failed to fetch VLANs").Err()
  	}
  	t.computeChanges(c, cfgs)
  	if err := t.add(c); err != nil {
  		return errors.Annotate(err, "failed to add VLANs").Err()
  	}
  	if err := t.remove(c); err != nil {
  		return errors.Annotate(err, "failed to remove VLANs").Err()
  	}
  	if err := t.update(c); err != nil {
  		return errors.Annotate(err, "failed to update VLANs").Err()
  	}
  	return nil
  }
docs: // EnsureVLANs ensures the database contains exactly the given VLANs.