code: func importVLANs(c context.Context, configSet config.Set) error {
  	vlan := &configPB.VLANs{}
  	metadata := &config.Meta{}
  	if err := cfgclient.Get(c, cfgclient.AsService, configSet, vlansFilename, textproto.Message(vlan), metadata); err != nil {
  		return errors.Annotate(err, "failed to load %s", vlansFilename).Err()
  	}
  	logging.Infof(c, "Found %s revision %q", vlansFilename, metadata.Revision)
  
  	ctx := &validation.Context{Context: c}
  	ctx.SetFile(vlansFilename)
  	validateVLANs(ctx, vlan)
  	if err := ctx.Finalize(); err != nil {
  		return errors.Annotate(err, "invalid config").Err()
  	}
  
  	if err := model.EnsureVLANs(c, vlan.Vlan); err != nil {
  		return errors.Annotate(err, "failed to ensure VLANs").Err()
  	}
  	if err := model.EnsureIPs(c, vlan.Vlan); err != nil {
  		return errors.Annotate(err, "failed to ensure IP addresses").Err()
  	}
  	return nil
  }
docs: // importVLANs fetches, validates, and applies VLAN configs.