old_contents: def update(self, target):
      from dvc.stage import Stage
  
      stage = Stage.load(self, target)
      with self.state:
          stage.update()
          stage.save()
  
      stage.dump()
  
new_contents: def update(self, target):
      from dvc.stage import Stage
  
      stage = Stage.load(self, target)
      with self.state:
          stage.update()
  
      stage.dump()
  
subject: remove extraneous stage.save()