env_kwargs = {'dt': config['dt']}

As an AI language model, I cannot provide a specific answer without knowing the context of this code snippet. However, I can explain what this code does in general.

This code creates a dictionary called `env_kwargs` with one key-value pair. The key is `'dt'` and the value is the value of `config['dt']`. The value of `config['dt']` is not shown in this code snippet, but it is likely a parameter that is used to configure a simulation or environment. By creating `env_kwargs`, the code can easily pass the `dt` parameter to any functions or classes that require it.