code: def generate_nan_observation(obs_space: gym.Space) -> Any:
      """The NaN observation that indicates the environment receives no seed.
  
      We assume that obs is complex and there must be something like float.
      Otherwise this logic doesn't work.
      """
  
      sample = obs_space.sample()
      sample = fill_invalid(sample)
      return sample
  
imports: from __future__ import annotations
  import copy
  import warnings
  from contextlib import contextmanager
  from typing import Any, Callable, Dict, Generator, List, Optional, Set, Tuple, Type, Union, cast
  import gym
  import numpy
  from tianshou.env import BaseVectorEnv, DummyVectorEnv, ShmemVectorEnv, SubprocVectorEnv
  from qlib.typehint import Literal
  from .log import LogWriter
label_desc: Use image node_id 3 for calling a global function with example usage: generate_nan_observation(obs_space) and returns: sample