[BUG] minor `typing.ClassVar` fix for class variables of `Index` #4560

	name: type checking

	on:
	push:
	branches:
	- main
	pull_request:
	paths:
	- yt/*/.py
	- pyproject.toml
	- requirements/typecheck.txt
	- .github/workflows/type-checking.yaml
	workflow_dispatch:

	jobs:
	build:
	runs-on: ubuntu-latest
	name: type check
	timeout-minutes: 60

	concurrency:
	# auto-cancel any in-progress job on the same branch
	group: ${{ github.workflow }}-${{ github.ref }}
	cancel-in-progress: true

	steps:
	- name: Checkout repo
	uses: actions/checkout@v4

	- name: Set up Python
	uses: actions/setup-python@v5
	with:
	# run with oldest supported python version
	# so that we always get compatible versions of
	# core dependencies at type-check time
	python-version: '3.10'

	- name: Build
	run: \|
	python3 -m pip install --upgrade pip
	python3 -m pip install -e . -r requirements/typecheck.txt

	- run: python -m pip list

	- name: Run mypy
	run: mypy yt

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