TypeError: must be str, not NoneType

[moonsh]

Hi, I got this error when I typed "python -m sandbox.mack.run_simple" in the multiagent-Gail folder.

Traceback (most recent call last):
File "C:\Users\Seonghyeon.conda\envs\cv\lib\runpy.py", line 193, in _run_module_as_main
"main", mod_spec)
File "C:\Users\Seonghyeon.conda\envs\cv\lib\runpy.py", line 85, in _run_code
exec(code, run_globals)
File "D:\github_test\multiagent-gail\multiagent-gail\sandbox\mack\run_simple.py", line 63, in
main()
File "C:\Users\Seonghyeon.conda\envs\cv\lib\site-packages\click\core.py", line 764, in call
return self.main(*args, **kwargs)
File "C:\Users\Seonghyeon.conda\envs\cv\lib\site-packages\click\core.py", line 717, in main
rv = self.invoke(ctx)
File "C:\Users\Seonghyeon.conda\envs\cv\lib\site-packages\click\core.py", line 956, in invoke
return ctx.invoke(self.callback, **ctx.params)
File "C:\Users\Seonghyeon.conda\envs\cv\lib\site-packages\click\core.py", line 555, in invoke
return callback(*args, **kwargs)
File "D:\github_test\multiagent-gail\multiagent-gail\sandbox\mack\run_simple.py", line 58, in main
train(logdir + '/exps/mack/' + env_id + '/l-{}-b-{}/seed-{}'.format(lr, batch_size, seed),
TypeError: must be str, not NoneType