[BUG] TransformedEnv does not copy env properties

[matteobettini]

When wrapping an env in TransofrmedEnv, its properties are changed

from torchrl.envs import VmasEnv, RewardSum, TransformedEnv

if __name__ == "__main__":
    env = VmasEnv("balance", num_envs=3)
    print(env._allow_done_after_reset)
    t_env = TransformedEnv(env, RewardSum())
    print(t_env._allow_done_after_reset)

True
False

[vmoens]

Is this a generic bug or just specific to _allow_done_after_reset?

Not sure it's really a bug in general, there are instances where one would like to have different attributes in the transformed env and in the env.
For some (eg _allow_done_after_reset?) we can have fallbacks if we're confident that there is no reason for TransformedEnv to have a different behaviour. It's already the case for batch_size, device, run_type_checks and others.

For instance, I can imagine that if one is using the no-op transform she expects the behaviour of _allow_done_after_reset to change.

[matteobettini]

We can default to the attribute value in the original env and the specific transforms can change it.

I think it is counterintuitive that, if the transform does not need to change the property, the wrapper changes it.

Not sure if it is just specific to this