code: func (e *Ref) Proto() *api.Ref {
  	return &api.Ref{
  		Name:       e.Name,
  		Package:    e.Package.StringID(),
  		Instance:   common.InstanceIDToObjectRef(e.InstanceID),
  		ModifiedBy: e.ModifiedBy,
  		ModifiedTs: google.NewTimestamp(e.ModifiedTs),
  	}
  }
docs: // Proto returns cipd.Ref proto with information from this entity.