Changes visualize driver functions to return graphviz object

[skrawcz]

This change is backwards compatible. It returns and wires through returning the graphviz object created. That way in a notebook, it can render the DAG for you.

It also makes saving to a file optional -- you just need to pass in None explicitly. Adds test for it.

The hello world example is also updated with a real notebook and shows Thierry Jean's approach of using the autoreload extensions.

Changes

• returns graphviz object from display functions
• changes hello world to include a proper notebook

How I tested this

• via notebook
• unit tests

Notes

Checklist

• PR has an informative and human-readable title (this will be pulled into the release notes)
• Changes are limited to a single goal (no scope creep)
• Code passed the pre-commit check & code is left cleaner/nicer than when first encountered.
• Any change in functionality is tested
• New functions are documented (with a description, list of inputs, and expected output)
• Placeholder code is flagged / future TODOs are captured in comments
• Project documentation has been updated if adding/changing functionality.

[skrawcz]

[elijahbenizzy]

LGTM -- a few minor points