Consolidate typing for coords with Coords and StrongCoords aliases (fixes #7972)

[aman-coder03]

this PR addresses issue #7972 by consolidating the typing of coords across the PyMC codebase.

Previously, coords appeared with a mix of types such as:

• Sequence
• Sequence | np.ndarray
• dict[str, Any]

this PR introduces explicit and consistent type aliases:

• CoordValue
• Coords
• StrongCoordValue
• StrongCoords

(similar to the existing Shape, Dims, and StrongDims aliases in shape_utils)

Key changes

• standardizes Model.coords to return StrongCoords
• updates ArviZ conversion to return StrongCoords instead of dict[str, Any}
• removes the mixed use of Sequence, Sequence | np.ndarray, and untyped dictionaries
• improves static typing and downstream library compatibility

Notes

while testing this change, a runtime circular import involving: pymc.model.core pymc.distributions.shape_utils from pymc.model import modelcontext pymc.model (partially initialized) was encountered.

Fixes #7972

[aman-coder03]

@ricardoV94 it would be really helpful if you could review the changes!

[ricardoV94]

I'll ping some folks who are bigger fans of type-hints than me for review.

A whole new file seems a bit cluttering, although it could be useful to move more things in the future. My gut feeling would be to just throw this into one of the utils.py files for now.

[aman-coder03]

@ricardoV94 Thanks for the feedback!! I have implemented the changes!!

[williambdean]

Thoughts on a pymc.typing module?

from pymc.typing import Coords
import pymc as pm


coords: Coords = {"covariate": ["A", "B", "C"]}
model = pm.Model(coords=coords)

Or directly from pm

Seems out of place in the utils module.

[ricardoV94]

What would go in it? If it's just a handful doesn't seem worth it

[codecov[bot]]

Codecov Report

:x: Patch coverage is 97.95918% with 1 line in your changes missing coverage. Please review. :white_check_mark: Project coverage is 91.50%. Comparing base (87f80f9) to head (27b010d). :warning: Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
pymc/distributions/shape_utils.py	93.33%	1 Missing :warning:

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7987   +/-   ##
=======================================
  Coverage   91.49%   91.50%           
=======================================
  Files         116      116           
  Lines       18963    18992   +29     
=======================================
+ Hits        17350    17378   +28     
- Misses       1613     1614    +1     

Files with missing lines	Coverage Δ
pymc/backends/arviz.py	96.09% <100.00%> (+0.04%)	:arrow_up:
pymc/model/core.py	93.30% <100.00%> (ø)
pymc/printing.py	87.66% <100.00%> (+0.16%)	:arrow_up:
pymc/step_methods/state.py	95.52% <100.00%> (ø)
pymc/util.py	82.18% <100.00%> (+1.07%)	:arrow_up:
pymc/distributions/shape_utils.py	91.41% <93.33%> (-0.47%)	:arrow_down:

... and 1 file with indirect coverage changes

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• :snowflake: Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[aman-coder03]

Thanks for the feedback! @ricardoV94 @williambdean

Right now it’s just the coord/shape aliases (Coords, CoordValue, StrongCoords, etc.). So I agree it might feel too small to justify a standalone pymc.typing module at the moment.

Reason for grouping them was: They do not really fit semantically into util.py They are used across several modules (model, backends, shape_utils) A dedicated namespace keeps things cleaner as more typing-related additions come in later

But I'm also happy to keep everything inside pymc.util Let me know which direction you would like, and I will update the PR accordingly.

[aman-coder03]

@ricardoV94 @williambdean i have implemented some changes, it would be really helpful if you take a look!!

[aman-coder03]

can you please guide me on the basis of the latest commit? @michaelosthege