Fix the errors when only some feature columns are constants for `wdud` #1343

	name: CI Tox

	on:
	# GitHub has started calling new repo's first branch "main" https://github.com/github/renaming
	# Existing codes likely still have "master" as the primary branch
	# Both are tracked here to keep legacy and new codes working
	push:
	branches:
	- "master"
	- "main"
	pull_request:
	branches:
	- "master"
	- "main"
	schedule:
	# Nightly tests run on master by default:
	# Scheduled workflows run on the latest commit on the default or base branch.
	# (from https://help.github.com/en/actions/reference/events-that-trigger-workflows#scheduled-events-schedule)
	- cron: "0 0 * * *"

	jobs:
	test:
	name: Test on ${{ matrix.os }}, Python ${{ matrix.python-version }}
	runs-on: ${{ matrix.os }}
	strategy:
	matrix:
	# os: [macOS-latest, windows-latest, ubuntu-latest]
	os: [macos-13, windows-latest, ubuntu-latest]
	python-version: ["3.9", "3.10", "3.11"]

	steps:
	- uses: actions/checkout@v4
	- name: Additional info about the build
	shell: bash
	run: \|
	uname -a
	df -h
	ulimit -a

	- name: Set up Python ${{ matrix.python-version }}
	uses: actions/setup-python@v5
	with:
	python-version: ${{ matrix.python-version }}
	architecture: x64

	- name: Install dependencies
	shell: bash
	run: \|
	python -m pip install --upgrade pip
	python -m pip install -r requirements_dev.txt
	# python -m pip install -U pytest pytest-cov codecov
	python -m pytest -c pyproject.toml --cov-config=.coveragerc --cov-report=xml --color=yes selector

	- name: Install package
	shell: bash
	run: \|
	python -m pip install .
	pip install tox tox-gh-actions

	- name: Run tests
	shell: bash
	run: \|
	tox

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