code: func (r *gceProjectRouter) ProjectID(ctx context.Context, version meta.Version, service string) string {
  	switch service {
  	case "Firewalls", "Routes":
  		return r.gce.NetworkProjectID()
  	default:
  		return r.gce.projectID
  	}
  }
docs: // ProjectID returns the project ID to be used for the given operation.