Set the 'colab' renderer only for Colab web notebooks

[kevineger]

Full context in #5471.

The current implementation detects if the google.colab module is available. This has a couple problems:

1. Anyone can install that library, outside of Colab.
2. The recently launched Colab VS Code extension does not work with that web-based renderer.

Snapping to the conventions used for the other notebooks/renderers (e.g. Kaggle, Azure), this change now looks for the presence of the COLAB_NOTEBOOK_ID environment variable. I'm an engineer on Colab and have verified that we set this on kernel init for all notebooks accessed through our web app (https://colab.research.google.com/).

Code PR

• I have read through the contributing notes and understand the structure of the package. In particular, if my PR modifies code of plotly.graph_objects, my modifications concern the code generator and not the generated files.
• I have added tests or modified existing tests.
  • Added test.
  • Added regression test for old import approach.
• For a new feature, I have added documentation examples (please see the doc checklist as well).
  • Not a new feature.
• I have added a CHANGELOG entry if changing anything substantial.
  • Added, as requested.
• For a new feature or a change in behavior, I have updated the relevant docstrings in the code.
  • Not a substantial feature change. I can update any docs if requested.

[kevineger]

Hey @robertclaus and @camdecoster - mind taking a look or re-assigning? Let me know if any further action's needed on my end to move this along.

Thanks and sorry for the nag!

[camdecoster]

@kevineger could you give me some instructions for how to test this? I'm not familiar with the Colab extension.

[kevineger]

@kevineger could you give me some instructions for how to test this? I'm not familiar with the Colab extension.

@camdecoster you could package this up and run a local Colab runtime (docs).

[camdecoster]

@kevineger I verified your changes work for setting the renderer when the COLAB_NOTEBOOK_ID env var is present. Before this gets merged, could you please add a test in tests/test_io/test_renderers.py? After that's done, could you tag me in a comment?

EDIT: Could you also please add a changelog entry?

[kevineger]

Done and done @camdecoster ✔️

Let me know if there's a better way to test than what I did.