Install the development version using pip:
pip install -e .
Don't forget the period.
Make sure you have WGMS3D installed first and that the compiled program is accessible to your $PATH.
@misc{hammond_pymode_2019,
title={pyMode},
author={Alec M. Hammond},
year={2019},
publisher={GitHub},
howpublished={{https://github.com/smartalecH/pyMode}}
}