add Column.len, which returns Scalar, instead of Column.len (returning int) #489

# to view logs

	name: lint

	on:
	pull_request:
	push:
	branches: [main]

	jobs:
	lint:
	strategy:
	matrix:
	python-version: ["3.8", "3.11"]
	os: [ubuntu-latest]

	runs-on: ${{ matrix.os }}
	steps:
	- uses: actions/checkout@v3
	- uses: actions/setup-python@v4
	with:
	python-version: ${{ matrix.python-version }}
	- name: Cache multiple paths
	uses: actions/cache@v3
	with:
	path: \|
	~/.cache/pip
	$RUNNER_TOOL_CACHE/Python/*
	~\AppData\Local\pip\Cache
	key: ${{ runner.os }}-build-${{ matrix.python-version }}
	- name: install-reqs
	run: python -m pip install --upgrade mypy typing-extensions ruff
	- name: run mypy
	run: cd spec/API_specification && mypy dataframe_api && mypy examples
	- name: run ruff format
	run: cd spec/API_specification && ruff format dataframe_api examples --diff
	- name: run ruff check
	run: cd spec/API_specification && ruff check dataframe_api examples --no-fix

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