### 🐛 Bug When launching an environment in multi-process, graphs cannot find the engine implementation for subjects, because objects are not reloaded. ### To Reproduce Launch an environment in a separate process ### Expected behavior No error. ### Checklist - [x] I have checked that there is no similar [issue](https://github.com/eager-dev/eagerx/issues) in the repo (**required**) - [x] I have read the [documentation](https://eagerx.readthedocs.io) (**required**) - [x] I have provided a minimal working example to reproduce the bug (**required**) <!--- This Template is an edited version of the one from https://github.com/DLR-RM/stable-baselines3-->