singleagent.py: user warning. Recommends transition from Open AI gym env to gymnasium env

[RibhavOjha]

Hi I get the following warning:

UserWarning: You provided an OpenAI Gym environment. We strongly recommend transitioning to Gymnasium environments. Stable-Baselines3 is automatically wrapping your environments in a compatibility layer, which could potentially cause issues.

I am aware that support for Gym has been discontinued, and they recommend using the gymnasium instead, but how is it specifically impacting gym-pybullet-drones?

Can I please get any help regarding this? I think this warning is causing further errors in the code in singleagent.py.

TypeError: empty() received an invalid combination of arguments - got (tuple, dtype=NoneType, device=NoneType), but expected one of:

• (tuple of ints size, *, tuple of names names, torch.memory_format memory_format, torch.dtype dtype, torch.layout layout, torch.device device, bool pin_memory, bool requires_grad)
• (tuple of ints size, *, torch.memory_format memory_format, Tensor out, torch.dtype dtype, torch.layout layout, torch.device device, bool pin_memory, bool requires_grad)

[JacopoPan]

Which branch/example are you getting this warning from? (See #169 #168)