Data Container core and Line2D - #32334

PR summary

This is the first PR towards the Data container project.

Reviewer Guide:

I would suggest starting with the architecture guide in users_explain. This provides an overview of each of the parts that are included and a sense of how they all fit together. (also please do tell me if there is a better place for it, this was alongside some of the other architectural descriptions I thought, but very willing to move it)

From there, I would suggest reviewing the code implementing the core pieces:

• containers.py - the implementation of the Data Containers themselves
• DataContainer as a Protocol
• ArrayContainer - for relatively static array data
• FuncContainer - which allows using functions... This is the most complex part of the file
• description.py - Desc objects and validations/interactions thereof
• conversion_edge.py - Implementation of Edges, and the execution graph
  • Note that the execution graph does touch on some utility that is underutilized in the initial roll out (weights on edges, default values, etc) These were left in to both ensure compatibility with the separately distributed PyPI package and because they are at least anticipated to be useful in internal usage
  • Look at the definition of an Edge
  • Subtypes of edge that provide specific functionality
    • SequenceEdge - chaining of edges to produce one logical "Edge"
    • CoordinateEdge - allows changing coordinates without changing values
    • DefaultEdge - providing default values
    • FuncEdge - arbitrary python functions
    • TransformEdge - represent Matplotlib Transforms
  • Review the Graph
    • __init__ does some precomputations which separate out subgraphs that are independant, this may be mildly confusing at first, but prevents a lot of looping through large lists of edges that have nothing to do with what you are computing
    • evaluator is the primary method of Graph, ultimately it is Djikstra's algorithm with a few tweaks on the input/output side

Finally, reviewing the implementation within Line2D, my rough outline for points to particularly focus on for review:

• LineContainer - a simple container that allows for checking/backwards compatibility operations
• Initialization to an empty container
• Remapping of private caching properties (_x, _y, _xorig, _yorig_, _xy)
• set_data and related functionality should work as existing users expect, but is not available if you provide your own container, as once you opt in to using a new container, that container becomes responsible for updating the data
• draw functionality

I would include the functionality of _helpers.py as it comes up, there are only two things in there though:

• _get_graph - Builds a minimal Graph from a given Axes, which consists of only TransformEdges
• check_container - helper validation for backwards compatibility operations

AI Disclosure

None

PR quality check

• Use an expressive title, e.g. "Fix title font property precedence"
• New and changed code is tested
• Plotting related features are demonstrated in an example
• New features and API changes have release notes
• Documentation complies with general and docstring guidelines