code: func (ps *PaperSize) Copy() (*PaperSize, error) {
  	c := C.gtk_paper_size_copy(ps.native())
  	if c == nil {
  		return nil, nilPtrErr
  	}
  	t := &PaperSize{c}
  	runtime.SetFinalizer(t, (*PaperSize).free)
  	return t, nil
  }
docs: // Copy() is a wrapper around gtk_paper_size_copy().