clustering-index.go
func (index *ClusteringIndex) Add(point Point) {
	index.streetLevel.Add(point)
	index.cityLevel.Add(point)
	index.worldLevel.Add(point)
}
func (index *ClusteringIndex) Add(point Point) {
	index.streetLevel.Add(point)
	index.cityLevel.Add(point)
	index.worldLevel.Add(point)
}
func ( index * ClusteringIndex ) Add ( point Point ) { index . streetLevel . Add ( point ) index . cityLevel . Add ( point ) index . worldLevel . Add ( point ) }
// Add adds a point.
Add adds a point .