VitessceConfig.to_python method

[keller-mark]

From @mccalluc in the Spatial Omics Meeting Agenda:

The SDK is procedural: It takes a series of statements and assignments to temporary variables to create the desired viewconf. The object we have at the end gives us no way to get the sequence of operations necessary to create the object.
This makes idiomatic notebook generation difficult: All we can do is serialize to the JSON view-conf, but we've lost all the readability of the SDK

...

Three proposals, none of them easy:
• Walk the JSON viewconf, and try to identify substructures that can be created with the SDK.
• In the portal-ui code, instead of using the SDK directly, use something like the Command Pattern to build up the sequence of statements that can either be executed, or dropped into the notebook.
• Move the SDK from a procedural to a functional style, so that the repr for an object is executable code that will reproduce the object.

I wrote my understanding of the problem in the meeting agenda document. Building on your PR #66, in this PR I added a .to_python method for VitessceConfig instances. Running vc.to_python generates Python code that can be used to reconstruct the view config. It is kind of a hybrid of proposals 1 and 3 above. I added an example notebook at docs/notebooks/config_to_python.ipynb. Would this solution work for the notebook generation use case?

Also:
Fixes #63
Fixes #54
Fixes #62

[mccalluc]

Lots of comments on the trees, not really understanding the forest.

Rather than test on the structure of the reconstructed_vc_dict, I'd be interested to see a check on the actual output of to_python.

Did you consider building the python as a syntax tree, rather than as a string? It would be harder, no doubt, but it would give us a better guarantee that the structure is good.

[mccalluc]

I think it would be good to clarify with Nils what precisely he wants from the generated node that the json doesn't offer. One thing he might be looking for is avoiding cases like this where the same uuid string is incorporated as multiple points in the code... which might be tricky. Or maybe it's enough to get it into the python syntax and avoid the extra quotes around everything.

[mccalluc]

Also: This is awesome! Thank you so much for taking it on.

[mccalluc]

More thoughts!