[Python] Cannot find reference 'xxx' in __init__.py

I have a project in PyCharm organized as follows:

-- Sources
|--__init__.py
|--Calculators
|--__init__.py
|--Filters.py
|--Controllers
|--__init__.py
|--FiltersController.py
|--Viewers
|--__init__.py
|--DataVisualization.py
|--Models
|--__init__.py
|--Data


All of my __init__.py, except for the one right above Sources are blank files. I am receiving a lot of warnings of the kind:

Cannot find reference 'xxx' in __init__.py
​

For example, my FiltersController.py has this piece of code:

import numpy.random as npr

bootstrap = npr.choice(image_base.data[max(0, x-2):x+3, max(0, y-2):y+3].flatten(), size=(3, 3), replace=True)


And I get this warning:

Cannot find reference 'choice' in __init__.py
​

I'm googling wondering what does this mean and what should I do to code properly in Python.

Continue reading...