[Feature Request] Adding locals as an available attribute in callbacks

🚀 Feature

In methods inside BaseCallback like _on_step, passing locals_ can be extremely helpful when there’s a need to override some default behaviour.

Motivation

In this particular case, I’m looking to override some default action structure to fit to a custom(unfortunately can’t disclose any code) environment - for which a clean approach is to use callbacks, but I need access to the actions of the policy before being passed onto env.step()

Pitch

Access to locals passed into the callback on policy and environment related methods in the BaseCallback

### Checklist

• I have checked that there is no similar issue in the repo (required)

Thanks a lot, in advance! Apologies if this has been discussed elsewhere, couldn’t find it myself.

[ReHoss]

A quick way to see the relevant variable in your algorithm of choice is simply print all the keys in the self.locals.

class CustomCallback(BaseCallback):
    def _on_step(self):
        print(self.locals.keys()) # key's should contain 'actions' or the attribute you want to monitor
        # log the attribute self.locals['attribute_name']

In this case it might be easier to check and monitor each key with _actions in it to be algo agnostic, but there can be multiple of them. @ReHoss

Thanks I was going to inspect self.locals in my given context.

[ReHoss]

Yep I got it thank you:)