code: func lintMetricUnits(mf dto.MetricFamily) []Problem {
  	var problems problems
  
  	unit, base, ok := metricUnits(*mf.Name)
  	if !ok {
  		// No known units detected.
  		return nil
  	}
  
  	// Unit is already a base unit.
  	if unit == base {
  		return nil
  	}
  
  	problems.Add(mf, fmt.Sprintf("use base unit %q instead of %q", base, unit))
  
  	return problems
  }
docs: // lintMetricUnits detects issues with metric unit names.