code: func (ps *PluralSpec) Plural(number interface{}) (Plural, error) {
  	ops, err := newOperands(number)
  	if err != nil {
  		return Invalid, err
  	}
  	return ps.PluralFunc(ops), nil
  }
docs: // Plural returns the plural category for number as defined by
  // the language's CLDR plural rules.