Fix `ValueError: Invalid fmt` with `Structure.to(fmt='yml')` #5972

	name: Linting

	on:
	push:
	branches: [master]
	pull_request:
	branches: [master]

	permissions:
	contents: read

	jobs:
	lint:
	runs-on: ubuntu-latest
	steps:
	- uses: actions/checkout@v4

	- name: Set up Python
	uses: actions/setup-python@v5
	with:
	python-version: "3.9"

	- name: Install dependencies
	run: \|
	pip install --upgrade ruff mypy

	- name: ruff
	run: \|
	ruff --version
	ruff .
	ruff format --check .

	- name: mypy
	run: \|
	mypy --version
	rm -rf .mypy_cache
	mypy ${{ github.event.repository.name }}

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