code: func (points *PointsIndex) Add(point Point) {
  	points.Remove(point.Id())
  	newSet := points.index.AddEntryAt(point).(set)
  	newSet.Add(point.Id(), point)
  	points.currentPosition[point.Id()] = point
  }
docs: // Add adds a point to the index. If a point with the same Id already exists it gets replaced.