Fix typing errors & introduce mypy as a required CI step (#501) #4

	name: Lint
	on:
	push:
	paths:
	- '*.py'

	jobs:
	mypy:
	runs-on: ubuntu-latest
	steps:
	- name: Checkout
	uses: actions/checkout@v3
	- name: Setup Python
	uses: actions/setup-python@v4
	with:
	python-version: '3.11'
	cache: 'pip'
	- name: Install pipenv
	run: python -m pip install --upgrade pipenv wheel
	# TODO: add caching of Pipfile.lock
	- name: Install dependencies
	run: pipenv install --dev --deploy
	- name: Run mypy
	run: pipenv run mypy .

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