text: Title: Error for replace() when self.plan is a list
  Body: At [string formatting in flows.py for self.plan](https://github.com/microsoft/UFO/blob/8be10dc4c73963c6c7b316668647b0dea4b661e3/ufo/module/flow.py#L115C22-L115C104) there is a .replace() operation called. 
  Sometimes the model returns self.plan as a list. In such cases an error is thrown because replace cannot be called on a list. Most of the time self.plan is a string so it's only happening sometimes and hard to reproduce.
  
  