Sushant S

Fix `env_checker.py`

2

## Description ## Motivation and Context - [x] I have raised an issue to propose this change ([required](https://github.com/DLR-RM/stable-baselines3/blob/master/CONTRIBUTING.md) for new features and bug fixes) closes #944 ## Types of changes...

[Bug] in `env_checker.py`

4

### 🐛 Bug When the `observation_space` is a `Dict`, only the keys in the `observation_space.spaces.keys()` are checked with the keys returned in the observation. If there is a key in...