code: func (po *Po) pluralForm(n int) int {
  	po.RLock()
  	defer po.RUnlock()
  
  	// Failure fallback
  	if po.pluralforms == nil {
  		/* Use the Germanic plural rule.  */
  		if n == 1 {
  			return 0
  		}
  		return 1
  	}
  	return po.pluralforms.Eval(uint32(n))
  }
docs: // pluralForm calculates the plural form index corresponding to n.
  // Returns 0 on error