Update force model and docs. #2400

	# This workflow will install Python dependencies, run tests and lint with a single version of Python
	# For more information see: https://help.github.com/actions/language-and-framework-guides/using-python-with-github-actions

	name: kgcnn_unit_tests

	on:
	push:
	branches: [ master ]

	jobs:
	build:
	runs-on: ubuntu-latest

	steps:
	- uses: actions/checkout@v2
	- name: Set up Python 3.9
	uses: actions/setup-python@v2
	with:
	# Semantic version range syntax or exact version of a Python version
	python-version: '3.9'
	# Optional - x64 or x86 architecture, defaults to x64
	architecture: 'x64'
	# You can test your matrix by printing the current Python version
	- name: Display Python version
	run: python -c "import sys; print(sys.version)"
	- name: Install dependencies
	run: \|
	python -m pip install --upgrade pip setuptools wheel
	pip install -r requirements.txt
	- name: Run unit tests
	run: \|
	python -m unittest discover

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