code: func (ps *PointSet) RemoveAt(index int) *PointSet {
  	deref := *ps
  	if index >= len(deref) || index < 0 {
  		panic(fmt.Sprintf("geo: remove index out of range, requested: %d, length: %d", index, len(deref)))
  	}
  
  	deref = append(deref[:index], deref[index+1:]...)
  	*ps = deref
  	return ps
  }
docs: // RemoveAt removes a Point at i in the point set.
  // Panics if index is out of range.