How to properly create package python : Say i have a folder named foo. Inside that folder is __init__.py, a folder called test, and a another python file called t1.py. Inside folder test is a python file called bar.py, and in that file I am trying to do something like: from foo import t1. And it gives me this error: ModuleNotFoundError: No module named 'gmuwork'. 
Do i need to add something to environment variables, or sys.path?