code: def redirect_subwindows(self, update, onerror = None):
      
      RedirectSubwindows(display = self.display,
                         onerror = onerror,
                         opcode = self.display.get_extension_major(extname),
                         window = self,
                         update = update,
                         )
docs: Redirect the hierarchies starting at all current and future
      children to this window to off-screen storage.