func (t *Tag) setUndefinedLang(id Language) {
	if t.LangID == 0 {
		t.LangID = id
	}
}

func (t *Tag) setUndefinedScript(id Script) {
	if t.ScriptID == 0 {
		t.ScriptID = id
	}
}

func (t *Tag) setUndefinedRegion(id Region) {
	if t.RegionID == 0 || t.RegionID.Contains(id) {
		t.RegionID = id
	}
}

// ErrMissingLikelyTagsData indicates no information was available
// to compute likely values of missing tags.