message: use deepcopy
diff: @@ -79,12 +79,15 @@ class Scenario:
  return self._build_world_state()
  def copy(self):
  + observer_model = None
  + if self._observer_model is not None:
  + observer_model = self._observer_model.deepcopy()
  return Scenario(agent_list=copy.deepcopy(self._agent_list),
  eval_agent_ids=self._eval_agent_ids.copy(),
  map_file_name=self._map_file_name,
  json_params=self._json_params.copy(),
  map_interface=self._map_interface,
  - observer_model=self._observer_model)
  + observer_model=observer_model)
  def _build_world_state(self):
  param_server = ParameterServer(json=self._json_params)
  