Add stochastic taxi (rainy+fickle)

[foreverska]

Description

Adds rainy transition probabilities and fickle passenger to align environment with paper.

Fixes #161

Type of change

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

Checklist:

• I have run the pre-commit checks with pre-commit run --all-files (see CONTRIBUTING.md instructions to set it up)
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[pseudo-rnd-thoughts]

Hey @foreverska, thanks for the PR.

Generally the PR looks good.
Could you change the np.random to self.np_random and revert the environment version increment (new features that don't affect default behaviour shouldn't require version bumps)

and a couple of questions before approving and merging

1. Is this backward compatible with default parameters? If it does currently, could we make it backward compatible.
2. Is the probability of the behaviour reported in step and reset correctly?

[foreverska]

@pseudo-rnd-thoughts

Addressed Comments.

Is this backward compatible with default parameters

Yes, default values for rainy and fickle are both False. This aligns functionality with pre-commit default behavior.

Is the probability of the behaviour reported in step and reset correctly?

It matches the other ToyText environments (Cliff/Frozen) with step returning the probability of the taken transition and reset always returning 1. I added lines in the unit test to guard against regression.

[pseudo-rnd-thoughts]

With the tests and documentation updates, then should be good to merge.
Thanks for making the changes

[Kallinteris-Andreas]

Looks good to me,

[foreverska]

@pseudo-rnd-thoughts I think this needs one more review since there was a commit after your last one. Thanks.

[pseudo-rnd-thoughts]

Hey @foreverska, sorry I'm on holiday currently. Looking over the PR again, I'm a tad worried about the is_rainy change.
Is there a way of making the code only run if is_rainy is true?