Can not copy a GymEnv environment when using a LightSim2Grid backend

[EBoguslawski]

Environment

• Python version: 3.12
• Grid2op version: 1.10.5
• LightSim2Grid version: 0.9.2.post2
• System: ubuntu

Bug description

Hello,

I create a GymEnv environment from a grid2op environment. If I use a LightSimBackend backend when creating the grid2op environment, then I obtain an error if I try to copy the GymEnv environment with copy.deepcopy.
It works on an older environment with older versions (python 3.8, Grid2op 1.9.8, LightSim2Grid 0.7.0.post1)

Notes:

• In the l2rpn_baselines.PPO_SB3.utils.SB3Agent class, a copy.deepcopy is performed on the nn_kwargs argument during initialization, the latter containing a GymEnv in its keys / values (needed to train the agent). Consequently, it now raises this error.
• I cannot find any copy method for the GymEnv class
• I firstly put this issue on the Grid2op repo, but was asked to copy it here. So this issue is a replicate of this one: Can not copy a GymEnv environment when using a LightSim2Grid backend grid2op#672

How to reproduce

Code snippet

import grid2op
from grid2op.gym_compat import GymEnv
from lightsim2grid import LightSimBackend
import copy

env = grid2op.make("l2rpn_case14_sandbox", backend=LightSimBackend())
env_gym = GymEnv(env)

# This line raises an error
copy.deepcopy(env_gym)

Current output

/data/boguslawskieva/virtual_environments/venv_multi_agent/lib/python3.12/site-packages/lightsim2grid/gridmodel/from_pandapower/_aux_add_trafo.py:38: UserWarning: There were some Nan in the pp_net.trafo["tap_neutral"], they have been replaced by 0
  warnings.warn("There were some Nan in the pp_net.trafo[\"tap_neutral\"], they have been replaced by 0")
/data/boguslawskieva/virtual_environments/venv_multi_agent/lib/python3.12/site-packages/lightsim2grid/gridmodel/from_pandapower/_aux_add_trafo.py:46: UserWarning: There were some Nan in the pp_net.trafo["tap_step_percent"], they have been replaced by 0
  warnings.warn("There were some Nan in the pp_net.trafo[\"tap_step_percent\"], they have been replaced by 0")
/data/boguslawskieva/virtual_environments/venv_multi_agent/lib/python3.12/site-packages/lightsim2grid/gridmodel/from_pandapower/_aux_add_trafo.py:51: UserWarning: There were some Nan in the pp_net.trafo["tap_pos"], they have been replaced by 0
  warnings.warn("There were some Nan in the pp_net.trafo[\"tap_pos\"], they have been replaced by 0")
/data/boguslawskieva/virtual_environments/venv_multi_agent/lib/python3.12/site-packages/lightsim2grid/gridmodel/from_pandapower/_aux_add_trafo.py:70: UserWarning: There were some Nan in the pp_net.trafo["tap_step_degree"], they have been replaced by 0
  warnings.warn("There were some Nan in the pp_net.trafo[\"tap_step_degree\"], they have been replaced by 0")
/data/boguslawskieva/virtual_environments/venv_multi_agent/lib/python3.12/site-packages/lightsim2grid/gridmodel/from_pandapower/_aux_add_slack.py:56: UserWarning: LightSim will not consider the pandapower "ext_grid" as there are already generators tagged as slack bus
  warnings.warn("LightSim will not consider the pandapower \"ext_grid\" as there "
Traceback (most recent call last):
  File "/home/boguslawskieva/env_with_setpoint_new_implementation/test.py", line 200, in <module>
    copy.deepcopy(env_gym)
  File "/usr/lib/python3.12/copy.py", line 162, in deepcopy
    y = _reconstruct(x, memo, *rv)
        ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/copy.py", line 259, in _reconstruct
    state = deepcopy(state, memo)
            ^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/copy.py", line 136, in deepcopy
    y = copier(x, memo)
        ^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/copy.py", line 221, in _deepcopy_dict
    y[deepcopy(key, memo)] = deepcopy(value, memo)
                             ^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/copy.py", line 162, in deepcopy
    y = _reconstruct(x, memo, *rv)
        ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/copy.py", line 259, in _reconstruct
    state = deepcopy(state, memo)
            ^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/copy.py", line 136, in deepcopy
    y = copier(x, memo)
        ^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/copy.py", line 221, in _deepcopy_dict
    y[deepcopy(key, memo)] = deepcopy(value, memo)
                             ^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/copy.py", line 162, in deepcopy
    y = _reconstruct(x, memo, *rv)
        ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/copy.py", line 259, in _reconstruct
    state = deepcopy(state, memo)
            ^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/copy.py", line 136, in deepcopy
    y = copier(x, memo)
        ^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/copy.py", line 221, in _deepcopy_dict
    y[deepcopy(key, memo)] = deepcopy(value, memo)
                             ^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/copy.py", line 143, in deepcopy
    y = copier(memo)
        ^^^^^^^^^^^^
  File "/data/boguslawskieva/virtual_environments/venv_multi_agent/lib/python3.12/site-packages/lightsim2grid/lightSimBackend.py", line 1418, in __deepcopy__
    result = self.copy()
             ^^^^^^^^^^^
  File "/data/boguslawskieva/virtual_environments/venv_multi_agent/lib/python3.12/site-packages/lightsim2grid/lightSimBackend.py", line 1531, in copy
    res._grid = mygrid.copy()
                ^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'copy'