code: def revert(self):
          
          if self.filepath:
              if path.isfile(self.filepath):
                  serialised_file = open(self.filepath, "r")
                  try:
                      self.state = json.load(serialised_file)
                  except ValueError:
                      print("No JSON information could be read from the persistence file - could be empty: %s" % self.filepath)
                      self.state = {}
                  finally:
                      serialised_file.close()
              else:
                  print("The persistence file has not yet been created or does not exist, so the state cannot be read from it yet.")
          else:
              print("Filepath to the persistence file is not set. State cannot be read.")
              return False
docs: Revert the state to the version stored on disc.