Cannot import GeographicPosition from simobility.core

[lijiawei20161002]

Get this error when running example: simple simulation.
ImportError: cannot import name 'GeographicPosition' from 'simobility.core' (~/venv/test.py/lib/python3.7/site-packages/simobility/core/init.py)

I'm using python 3.7, pycharm.