ENH: improve MinariDataset

[younik]

Description

Add __getitem__and __len__() to MinariDataset and few refactors.

Type of change

• New feature (non-breaking change which adds functionality)

Checklist:

• I have run the pre-commit checks with pre-commit run --all-files (see CONTRIBUTING.md instructions to set it up)
• I have run pytest -v and no errors are present.
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I solved any possible warnings that pytest -v has generated that are related to my code to the best of my knowledge.
• 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

[balisujohn]

Seems to run fine and produces a performant policy, I requested a few minor changes, and asked a few questions.

One more comment: It might be good to provide a requirements.txt for tutorials(though the version of Minari this will depend on isn't in a release yet, so I suppose it would have to be in a later PR)

[rodrigodelazcano]

I just added some suggestions

[balisujohn]

Really minor change requests, and a reminder that we should add a version locked requirements.txt after the next minari release. Otherwise, looks good, and ready to merge, assuming 500 is a good amount of total reward for the final cloned policy.

[balisujohn]

LGTM :^)

[rodrigodelazcano]

Looks good! Ready to merge