Support for graphviz rendering in outputs

[curtis-allan]

Description

This PR changes the render_outputs() function to support graphviz diagram outputs. The main problem was the order of return statements in render_output(), which was returning the text/plain data before being able to reach the image/svg+xml output type.

Since it's an image mimetype, I've moved the svg check into the include_imgs if statement check so the svg data is returned before any plain-text output.

Comparison

[gitnotebooks]

Found 1 changed notebook. Review the changes at https://app.gitnotebooks.com/AnswerDotAI/execnb/pull/73

[jph00]

This is looking good to me -- have you tested it @curtis-allan, and if so, is it ready to move out of draft now?

[curtis-allan]

@jph00 Yep - Added some inline tests to the notebook, can't see any reason it should cause issues outside of these niche cases.

Force-Pushed to fix CI errors & squash the history. Seems to be working well!

[jph00]

Thanks @curtis-allan . Those tests are too long and make it harder to read the nb. See the rest of the nb to get a sense of the style we're aiming for. Tests should be really minimal and just show the specific piece of functionality of interest. You probably don't want to be relying on LLMs to do this for you -- whilst they can help show ideas and direction, they're extremely verbose and don't care about wasting our time!

[curtis-allan]

Thanks for the feedback @jph00, will fix it up and rebase to a single commit :)

Edit: Tests for multipart mimebundles are already included in the NB, so decided it best to remove the extra test cases. Have tested in-depth my end and all looks good, was simply a case of display_data return order differing from Jupyter's mime-type rendering priority list.