class_docstr: Variant of CartPoleEnv with velocity information removed. This task requires memory to solve.
code: def step(self, action):
      full_obs, rew, done, info = super().step(action)
      return CartPoleNoVelEnv._pos_obs(full_obs), rew, done, info
  
imports: import os
  from gym.envs.classic_control import CartPoleEnv
  from gym.wrappers.time_limit import TimeLimit
  from gym import spaces
  import numpy
  import pytest
  from stable_baselines import A2C, ACER, ACKTR, PPO2, bench
  from stable_baselines.common.policies import MlpLstmPolicy, LstmPolicy
  from stable_baselines.common.vec_env import SubprocVecEnv
  from stable_baselines.common.vec_env.vec_normalize import VecNormalize
  from stable_baselines.common.math_util import safe_mean
  from stable_baselines.common.evaluation import evaluate_policy
label_desc: Use image node_id 4 for calling the CartPoleNoVelEnv obj's underlying member method code with example usage: obj.step(action) and returns: CartPoleNoVelEnv,  rew,  done,  info