code: def get_history_manager_for_model(model):
      
      try:
          manager_name = model._meta.simple_history_manager_attribute
      except AttributeError:
          raise NotHistoricalModelError(
              "Cannot find a historical model for {model}.".format(model=model)
          )
      return getattr(model, manager_name)
docs: Return the history manager for a given app model.