def undo(self):
        """Undo the last action.

        This will call `undo()` on all controllers involved in this action.

        """
        controllers = self.back()
        if controllers is None:
            ups = ()
        else:
            ups = tuple([controller.undo()
                        for controller in controllers])
        if self.process_ups is not None:
            return self.process_ups(ups)
        else:
            return ups
def undo ( self ) : controllers = self . back ( ) if controllers is None : ups = ( ) else : ups = tuple ( [ controller . undo ( ) for controller in controllers ] ) if self . process_ups is not None : return self . process_ups ( ups ) else : return ups
Undo the last action.

        This will call `undo()` on all controllers involved in this action.