Add callback documentation #1047

	name: CI

	on: [push, pull_request]

	jobs:
	test:
	runs-on: ${{matrix.os}}
	strategy:
	fail-fast: false
	matrix:
	os: [macOS-latest, ubuntu-latest, windows-latest]
	python-version: ["3.9"]
	steps:
	- uses: actions/checkout@v2
	- uses: actions/setup-node@v2
	- name: Set up Python
	uses: actions/setup-python@v2
	with:
	python-version: ${{ matrix.python-version }}
	- name: Install dependencies
	run: \|
	python -m pip install -U pip install wheel setuptools cffi
	- name: Download helics library and run pip install
	run: \|
	python setup.py download
	python setup.py build_ext
	pip install -e ".[tests]"
	- name: Install pytest dependencies
	run: \|
	pip install pytest pytest-ordering pytest-cov pytest-runner
	- name: Generate coverage report
	run: \|
	pytest -vvv --cov=./ --cov-report=xml:unit.coverage.xml
	- name: Upload unit test coverage to Codecov
	uses: codecov/codecov-action@v1
	with:
	token: ${{ secrets.CODECOV_TOKEN }}
	file: ./unit.coverage.xml
	flags: unit
	env_vars: PYTHON
	name: codecov-unit
	fail_ci_if_error: false

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