code: def _get_observer_fun(self, prop_name):
          
          def _observer_fun(self, model, old, new):
              if self._itsme:
                  return
              self._on_prop_changed()
  
          # doesn't affect stack traces
          _observer_fun.__name__ = "property_%s_value_change" % prop_name
          return _observer_fun
docs: This is the code for an value change observer