docs: improve NumPy-style docstrings in atlas_specific modules

[AlgoFoe]

Description

What is this PR

• Bug fix
• Addition of a new feature
• Other

Why is this PR needed?

• The codebase lacked consistent docstrings, making Sphinx autodoc output incomplete and hard to read.

What does this PR do?

• Adds/updates NumPy-style docstrings (module, class, method, function level) in atlas_specific modules.

References

• Part of Issue-96

How has this PR been tested?

• No functional changes, existing tests pass.

Is this a breaking change?

• No.

Does this PR require an update to the documentation?

• Yes.

Checklist:

• The code has been tested locally
• Tests have been added to cover all new functionality (unit & integration)
• The documentation has been updated to reflect any changes
• The code has been formatted with pre-commit

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.67%. Comparing base (bdcdf90) to head (87f30a5).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #468      +/-   ##
==========================================
+ Coverage   89.64%   89.67%   +0.03%     
==========================================
  Files          27       27              
  Lines        1313     1317       +4     
==========================================
+ Hits         1177     1181       +4     
  Misses        136      136              

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[Copilot]

Pull request overview

This PR improves Sphinx autodoc output by adding and standardizing NumPy-style docstrings (and some related typing annotations) across Allen Brain Atlas atlas_specific modules.

Changes:

• Added module-level docstrings and expanded function/method docstrings in Allen atlas streamline and gene-expression modules.
• Added/clarified type annotations for several helper functions and GeneExpressionAPI methods.
• Improved parameter/return documentation to better match NumPy docstring conventions.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
brainrender/atlas_specific/allen_brain_atlas/streamlines.py	Adds module docstring and expands docstrings/type hints for streamline download/conversion utilities.
brainrender/atlas_specific/allen_brain_atlas/gene_expression/ge_utils.py	Adds module docstring plus docstrings/type hints for cache/download/load helpers used by gene expression workflows.
brainrender/atlas_specific/allen_brain_atlas/gene_expression/api.py	Adds module/class/method docstrings and typing for the Allen gene expression API client.

Suppressed comments (1)

brainrender/atlas_specific/allen_brain_atlas/gene_expression/ge_utils.py:42

• The docstring return type currently says "str or bool", but the function only returns a path string or False. Tightening this to "str or False" improves the generated NumPy-style documentation.

    Returns
    -------
    str or bool
        Path to the cached folder if found, False if not cached.

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[AlgoFoe]

@IgorTatarnikov, I'm not sure why the CI actions are failing. Probably not related to the changes in this PR?