code: func (ps PointSet) String() string {
  	if len(ps) == 0 {
  		return "EMPTY"
  	}
  
  	buff := bytes.NewBuffer(nil)
  	fmt.Fprintf(buff, "MULTIPOINT(%g %g", ps[0][0], ps[0][1])
  
  	for i := 1; i < len(ps); i++ {
  		fmt.Fprintf(buff, ",%g %g", ps[i][0], ps[i][1])
  	}
  
  	buff.Write([]byte(")"))
  	return buff.String()
  }
docs: // String returns a string representation of the path.
  // The format is WKT, e.g. MULTIPOINT(30 10,10 30,40 40)
  // For empty paths the result will be 'EMPTY'.