Some minor touchup to preconditions and fix for minus. #375

	name: lint

	on:
	push:
	branches:
	- main
	pull_request:

	jobs:
	run:
	runs-on: ${{ matrix.os }}

	strategy:
	matrix:
	os: [ubuntu-latest]
	python-version: ["3.8", "3.9", "3.10", "3.11"]

	timeout-minutes: 30

	steps:
	- uses: actions/checkout@main
	- uses: actions/setup-python@main
	with:
	python-version: ${{ matrix.python-version }}
	- name: Install dependencies
	run: pip install tox
	- name: Code style check
	run: \|
	tox -e black-check
	tox -e isort-check
	tox -e flake8
	- name: Unused code check
	run: tox -e vulture
	- name: Static type check
	run: tox -e mypy
	- name: Check copyright
	run: tox -e check-copyright
	- name: Misc checks
	run: \|
	tox -e bandit
	tox -e safety

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