[Bug Report] Checking if the entire environment is done

[destin-v]

Describe the bug

According to the documentation:

"When an agent is terminated or truncated, it’s removed from agents, so when the environments done agents will be an empty list. This means not env.agents is a simple condition for the environment being done." - PettingZoo Doc

I tested this on connect_four_v3 and it does not work:

The env.agents will still have agents in the list even after all agents have terminated. This can be checked by conditioning a break point on all terminated agents.

Code example

import numpy as np
import pettingzoo
from pettingzoo.classic import connect_four_v3


def test_connect4():
    obs: dict[str, np.ndarray]
    termination: bool
    truncation: bool

    env: pettingzoo.AECEnv = connect_four_v3.env(render_mode="human")
    env.reset(seed=42)

    for agent in env.agent_iter():
        obs, _, termination, truncation, _ = env.last()  # type: ignore

        if termination or truncation:
            if len(env.agents) > 0:
                print(f"env.agents: {env.agents}")
                raise ValueError("env.agents should be empty!")

        mask = obs["action_mask"]
        # this is where you would insert your policy
        action = env.action_space(agent).sample(mask)

        env.step(action)

    env.close()

System info

Running on Intel based Macbook Pro 2019.

Additional context

No response

Checklist

• I have checked that there is no similar issue in the repo

[CreazeD]

I have the same problem