func (t Tag) IsPrivateUse() bool {
	return t.str != "" && t.pVariant == 0
}
IsPrivateUse reports whether the Tag consists solely of an IsPrivateUse use
tag.
package language  
import (
	"errors"
	"fmt"
	"strings"
)
const (
	maxCoreSize = 12
	max99thPercentileSize = 32
	maxSimpleUExtensionSize = 14
)
type Tag struct {
	LangID   Language
	RegionID Region
	ScriptID Script
	pVariant byte    
	pExt     uint16  
	str string
}
func Make(s string) Tag {
	t, _ := Parse(s)
	return t
}
func (t Tag) Raw() (b Language, s Script, r Region) {
	return t.LangID, t.ScriptID, t.RegionID
}
func (t Tag) equalTags(a Tag) bool {
	return t.LangID == a.LangID && t.ScriptID == a.ScriptID && t.RegionID == a.RegionID
}
func (t Tag) IsRoot() bool {
	if int(t.pVariant) < len(t.str) {
		return false
	}
	return t.equalTags(Und)
}