AssertionError: Tuple observations are not supported.

[robot-feng]

Bug description

Description of what the bug is.
AssertionError: Tuple observations are not supported.

Steps to reproduce

Code or a description of how to reproduce the bug.

import gymnasium as gym
import numpy as np
from stable_baselines3 import PPO
from stable_baselines3.common.evaluation import evaluate_policy
from stable_baselines3.ppo import MlpPolicy

from imitation.algorithms import bc
from imitation.data import rollout
from imitation.data.wrappers import RolloutInfoWrapper
from imitation.policies.serialize import load_policy
from imitation.util.util import make_vec_env

rng = np.random.default_rng(0)

env = gym.make("Pendulum-v1")
env = RolloutInfoWrapper(env)

def train_expert():
    print("Training a expert.")
    expert = PPO(
        policy=MlpPolicy,
        env=env,
        seed=0,
        batch_size=64,
        ent_coef=0.0,
        learning_rate=0.0003,
        n_epochs=10,
        n_steps=64,
    )
    expert.learn(10)  # Note: change this to 100_000 to train a decent expert.
    return expert

  
def sample_expert_transitions():
    expert = train_expert()
    print("Sampling expert transitions.")
    rollouts = rollout.rollout(
        expert,
        env,
        rollout.make_sample_until(min_timesteps=None, min_episodes=50),
        rng=rng,
    )
    return rollout.flatten_trajectories(rollouts)

Environment

• Operating system and version:
• Python version:
• Output of pip freeze --all: