provider/zone_tag_filter.go
func NewZoneTagFilter(tags []string) ZoneTagFilter {
	if len(tags) == 1 && len(tags[0]) == 0 {
		tags = []string{}
	}
	return ZoneTagFilter{zoneTags: tags}
}
func NewZoneTagFilter(tags []string) ZoneTagFilter {
	if len(tags) == 1 && len(tags[0]) == 0 {
		tags = []string{}
	}
	return ZoneTagFilter{zoneTags: tags}
}
// NewZoneTagFilter returns a new ZoneTagFilter given a list of zone tags