code: func (v *HeaderBar) SetSubtitle(subtitle string) {
  	cstr := C.CString(subtitle)
  	defer C.free(unsafe.Pointer(cstr))
  	C.gtk_header_bar_set_subtitle(v.native(), (*C.gchar)(cstr))
  }
docs: // SetSubtitle is a wrapper around gtk_header_bar_set_subtitle().