code: func CheckMetrics() int {
  	l := promlint.New(os.Stdin)
  	problems, err := l.Lint()
  	if err != nil {
  		fmt.Fprintln(os.Stderr, "error while linting:", err)
  		return 1
  	}
  
  	for _, p := range problems {
  		fmt.Fprintln(os.Stderr, p.Metric, p.Text)
  	}
  
  	if len(problems) > 0 {
  		return 3
  	}
  
  	return 0
  }
docs: // CheckMetrics performs a linting pass on input metrics.