clustering-index.go
func (index *ClusteringIndex) Remove(id string) {
	index.streetLevel.Remove(id)
	index.cityLevel.Remove(id)
	index.worldLevel.Remove(id)
}
func (index *ClusteringIndex) Remove(id string) {
	index.streetLevel.Remove(id)
	index.cityLevel.Remove(id)
	index.worldLevel.Remove(id)
}
// Remove removes a point.