code: func ProjectFromContext(ctx context.Context) (string, error) {
  	project, ok := ctx.Value(&luciProjectKey).(string)
  	if !ok {
  		return "", errors.Reason("LUCI project not available in context").Err()
  	}
  	if project == "" {
  		return "", errors.Reason("LUCI project is empty string").Err()
  	}
  	return project, nil
  }
docs: // ProjectFromContext is the opposite of WithProject, is extracts the
  // LUCI project which the current call stack is handling a request for.