Added doctests for better documentation and testing

[Ritunjai-Sharma]

PR for adding doctests to interpreter.py
Associated Issue: #11

The following work was done in this PR:

• Referred to notebooks in the example folder and added doctests to functions in interpreter.py
• Fixed a bug that I found while running doctests in interpreter.py.
• Updated pyproject.toml to include doctests

Notes for Reviewer

• This PR was created by branching off the feature/investigate_CI branch that was created for the Setup CI PR, to allow updated CI to work for this doctests PR. However, this means a lot of changes in this PR are from the Setup CI PR. So please note that the the reviewer only needs to review this commit for this PR.
• Note that the majority of the example doctests have been added to transform function in interpreter.py as this function is what the user will use to generate the outputs. I have included most of the example doctests showing different functionalities of the transform function in Binary classification (RandomForest / tree-based) section, which I have based off the binary_classification.ipynb notebook. I have still added some additional example doctests in Multiclass classification (based off multiclass_classification.ipynb), XGBoost regression (based off example.ipynb), One-hot encoding (based off example_ohe.ipynb) and Non-standard models (based off non_standard_model.ipynb) sections.
• Adding comprehensive example doctests to interpreter.py does mean it has bloated the script and made it quite large. However, at least now we have examples that get tested unlike the example notebooks that never get tested and can get outdated. But it would be good for the reviewer to have a look at interpreter.py with doctests added, from ease of readability POV and share their thoughts.

[cjmwills]

S: can we add details of this change to the changelog?

[cjmwills]

Q: should we instead be merging back into feature/investigate_CI branch if that PR hasn't been approved yet?

[Ritunjai-Sharma]

S: can we add details of this change to the changelog?

Added in this commit

[Ritunjai-Sharma]

Q: should we instead be merging back into feature/investigate_CI branch if that PR hasn't been approved yet?

I was thinking of just pulling changes into this branch from master once feature/investigate_CI is merged in? That way we can still merge this branch into master?

[cjmwills]

I was thinking of just pulling changes into this branch from master once feature/investigate_CI is merged in? That way we can still merge this branch into master?

Sounds good, in that case though we won't want to merge this until that PR has gone in. Otherwise we'll be merging unreviewed code into main.

[Ritunjai-Sharma]

I have now pulled latest changes from master into this branch in commit 9b8b3e8