code: func (p *OpenPrinter) Printer() *Printer {
  	if p.verify == nil {
  		panic(fmt.Errorf("Printer: VerifyClaim has not succeeded"))
  	}
  	return p.printer
  }
docs: // Printer returns information about the newly created printer.
  // This method is only a convenience: the returned printer is the
  // (only) one that would be returned by p.Server().Printers().
  //
  // Printer must be called only after VerifyClaim has succeeded.