deepcopy in python 3.6 giving:: rv = reductor(4) TypeError: 'NoneType' object is not callable

[SRaswan]

This is happening when using stable_baselines3 A2C to implement actor-critic agent and PPO agent.

Traceback (most recent call last):
File "/snap/pycharm-community/256/plugins/python-ce/helpers/pydev/pydevd.py", line 1483, in _exec
pydev_imports.execfile(file, globals, locals) # execute the script
File "/snap/pycharm-community/256/plugins/python-ce/helpers/pydev/_pydev_imps/_pydev_execfile.py", line 18, in execfile
exec(compile(contents+"\n", file, 'exec'), glob, loc)
File "/home/iman/GYM_XPLANE_ML/gym_xplane_final_version/examples/a2c_agent.py", line 76, in
main_a2c(env)
File "/home/iman/GYM_XPLANE_ML/gym_xplane_final_version/examples/a2c_agent.py", line 44, in main_a2c
model.learn(total_timesteps=100, callback=[checkpoint_callback, eval_callback])
File "/home/iman/miniconda3/envs/gym_xplane_final_version_py3.6/lib/python3.6/site-packages/stable_baselines3/a2c/a2c.py", line 201, in learn
reset_num_timesteps=reset_num_timesteps,
File "/home/iman/miniconda3/envs/gym_xplane_final_version_py3.6/lib/python3.6/site-packages/stable_baselines3/common/on_policy_algorithm.py", line 249, in learn
continue_training = self.collect_rollouts(self.env, callback, self.rollout_buffer, n_rollout_steps=self.n_steps)
File "/home/iman/miniconda3/envs/gym_xplane_final_version_py3.6/lib/python3.6/site-packages/stable_baselines3/common/on_policy_algorithm.py", line 179, in collect_rollouts
new_obs, rewards, dones, infos = env.step(clipped_actions)
File "/home/iman/miniconda3/envs/gym_xplane_final_version_py3.6/lib/python3.6/site-packages/stable_baselines3/common/vec_env/base_vec_env.py", line 162, in step
return self.step_wait()
File "/home/iman/miniconda3/envs/gym_xplane_final_version_py3.6/lib/python3.6/site-packages/stable_baselines3/common/vec_env/dummy_vec_env.py", line 51, in step_wait
return (self._obs_from_buf(), np.copy(self.buf_rews), np.copy(self.buf_dones), deepcopy(self.buf_infos))
File "/home/iman/miniconda3/envs/gym_xplane_final_version_py3.6/lib/python3.6/copy.py", line 150, in deepcopy
y = copier(x, memo)
File "/home/iman/miniconda3/envs/gym_xplane_final_version_py3.6/lib/python3.6/copy.py", line 215, in _deepcopy_list
append(deepcopy(a, memo))
File "/home/iman/miniconda3/envs/gym_xplane_final_version_py3.6/lib/python3.6/copy.py", line 150, in deepcopy
y = copier(x, memo)
File "/home/iman/miniconda3/envs/gym_xplane_final_version_py3.6/lib/python3.6/copy.py", line 240, in _deepcopy_dict
y[deepcopy(key, memo)] = deepcopy(value, memo)
File "/home/iman/miniconda3/envs/gym_xplane_final_version_py3.6/lib/python3.6/copy.py", line 169, in deepcopy
rv = reductor(4)
TypeError: 'NoneType' object is not callable