`TestPopulationSamplers` started failing in the CI

Description

FAILED tests/sampling/test_population.py::TestPopulationSamplers::test_checks_population_size - ValueError: setting an array element with a sequence.
FAILED tests/sampling/test_population.py::TestPopulationSamplers::test_demcmc_warning_on_small_populations - ValueError: setting an array element with a sequence.
FAILED tests/sampling/test_population.py::TestPopulationSamplers::test_nonparallelized_chains_are_random - ValueError: setting an array element with a sequence.
FAILED tests/sampling/test_population.py::TestPopulationSamplers::test_parallelized_chains_are_random - ValueError: setting an array element with a sequence.

Contributor guide

Tech stack

python

Domain

machine learningtesting

Issue type

bug

DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.

3

Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.

half day

Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.

fresh

ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.

mostly clear

Prerequisites

Pythonpytestnumpy

Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.

60

Research direction

The failing tests are in tests/sampling/test population.py. The error 'ValueError: setting an array element with a sequence' suggests a shape mismatch when constructing numpy arrays. Start by reproducing the issue locally with the same dependencies. Look at recent commits or dependency changes (e.g., numpy) that might have caused this. Inspect the test functions, particularly how population samples are generated, and ensure array inputs are properly shaped.