Add brain module for statistics inference

[emmanuel-ferdman]

Type of Changes

	Type
✓	🐛 Bug fix

Description

My first PR to astroid - hope the PR was implemented correctly.

This PR adds a new brain module brain_statistics.py that improves inference for statistics.quantiles() function calls. The statistics.quantiles() function has complex runtime behavior that returns lists with sizes dependent on the n parameter (specifically n-1 elements), but static analysis can only see the empty list initializations (result = []) in the function body and cannot follow the control flow that populates these lists. This causes astroid to infer empty lists, leading to false positives in pylint's unbalanced-tuple-unpacking checker. The brain module detects calls to statistics.quantiles() and returns Uninferable instead, allowing downstream tools to handle the "unknown size" case appropriately rather than acting on incorrect inference results.

Example:

import statistics

# This should work - statistics.quantiles(data, n=4) returns 3 quantiles
q1, q2, q3 = statistics.quantiles(list(range(100)), n=4)

Relevant Pylint issue: pylint-dev/pylint#10317

[codecov]

Codecov Report

❌ Patch coverage is 93.33333% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 93.36%. Comparing base (7c3b481) to head (558d070).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
astroid/brain/brain_statistics.py	93.10%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2832   +/-   ##
=======================================
  Coverage   93.36%   93.36%           
=======================================
  Files          91       92    +1     
  Lines       11115    11145   +30     
=======================================
+ Hits        10377    10406   +29     
- Misses        738      739    +1     

Flag	Coverage Δ
linux	93.23% <93.33%> (+<0.01%)	⬆️
pypy	93.36% <93.33%> (+<0.01%)	⬆️
windows	93.35% <93.33%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
astroid/brain/helpers.py	100.00% <100.00%> (ø)
astroid/brain/brain_statistics.py	93.10% <93.10%> (ø)

... and 1 file with indirect coverage changes

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[DanielNoord]

Nice addition!

Tests LGTM, only a comment about the use of hasattr

[DanielNoord]

Thanks!