* remove multibuf
* reward_metric
* make fileds with empty Batch rather than None after reset
* many fixes and refactor
Co-authored-by: Trinkle23897 <463003665@qq.com>
* Enable getattr for SubprovVecEnv.
* Consistent API between VectorEnv and SubprocVecEnv.
* Avoid code duplication. Add unit tests.
* Add docstring.
* Test more branches.
* Fix UT.
Co-authored-by: Alexis Duburcq <alexis.duburcq@wandercraft.eu>