add `len` to `CombinedConnection` #525

	name: pytest

	on:
	pull_request:
	push:
	branches:
	- main
	schedule:
	- cron: '14 3 * * 1' # at 03:14 on Monday.

	jobs:
	test:

	runs-on: ubuntu-latest
	strategy:
	fail-fast: false
	matrix:
	python-version: ["3.9", "3.10", "3.11", "3.12"]

	steps:
	- uses: actions/checkout@v2
	- name: Set up Python ${{ matrix.python-version }}
	uses: actions/setup-python@v2
	with:
	python-version: ${{ matrix.python-version }}
	- name: Install Poetry
	uses: abatilo/actions-poetry@v2
	with:
	poetry-version: 1.3.2
	- name: Install package
	run: \|
	poetry install --all-extras --without=notebook
	- name: Pytest
	run: \|
	poetry run coverage run -m pytest
	poetry run coverage lcov
	- name: Coveralls
	uses: coverallsapp/github-action@master
	with:
	github-token: ${{ secrets.GITHUB_TOKEN }}
	path-to-lcov: coverage.lcov

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