- [ ] I have marked all applicable categories:
    + [ ] exception-raising bug
    + [ ] RL algorithm bug
    + [ ] documentation request (i.e. "X is missing from the documentation.")
    + [ ] new feature request
- [ ] I have visited the [source website], and in particular read the [known issues]
- [ ] I have searched through the [issue tracker] for duplicates
- [ ] I have mentioned version numbers, operating system and environment, where applicable:
  ```python
  import tianshou, sys
  print(tianshou.__version__, sys.version, sys.platform)
  ```

  [source website]: https://github.com/thu-ml/tianshou/
  [known issues]: https://github.com/thu-ml/tianshou/#faq-and-known-issues
  [issue tracker]: https://github.com/thu-ml/tianshou/issues?q=