code: func (countIndex *CountIndex) Range(topLeft Point, bottomRight Point) []Point {
  	counters := countIndex.index.Range(topLeft, bottomRight)
  
  	points := make([]Point, 0)
  
  	for _, c := range counters {
  		if c.(counter).Point() != nil {
  			points = append(points, c.(counter).Point())
  		}
  	}
  
  	return points
  }
docs: // Range returns the counters within some lat, lng range.