Trying to [package](https://build.opensuse.org/package/show/home:badshah400:branches:science/python-pymathics-graph) this for openSUSE and I find that the following files are missing from the released tarballs, causing `pytest` to error out: * [`test/__init__.py`](../blob/master/test/__init__.py) * [`test/helper.py`](../blob/master/test/helper.py) Including these manually and then running `pytest` leads to success. Thanks for developing this library.