code: def _trigger_params_changed(self, trigger_parent=True):
          
          [p._trigger_params_changed(trigger_parent=False) for p in self.parameters if not p.is_fixed]
          self.notify_observers(None, None if trigger_parent else -np.inf)
docs: First tell all children to update,
          then update yourself.
  
          If trigger_parent is True, we will tell the parent, otherwise not.