code: func NewFromPointers(points []geo.Pointer) *Quadtree {
  	if len(points) == 0 {
  		// This is kind of meaningless but is what will happen
  		// if using an empty pointset above.
  		return New(geo.NewBound(0, 0, 0, 0))
  	}
  
  	b := geo.NewBoundFromPoints(points[0].Point(), points[0].Point())
  	for _, p := range points {
  		b.Extend(p.Point())
  	}
  
  	q := New(b, len(points))
  
  	for _, p := range points {
  		q.Insert(p)
  	}
  
  	return q
  }
docs: // NewFromPointers creates a quadtree from a set of pointers.