I have a project in Pycharm organized as follows:
-- Sources
|--__init__.py
|--Calculators
|--__init__.py
|--Filters.py
|--Controllers
This is a bug in pycharm. PyCharm seems to be expecting the referenced module to be included in an __all__ = [] statement.
For proper coding etiquette, should you include the __all__ statement from your modules? ..this is actually the question we hear young Spock answering while he was being tested, to which he responded: "It is morally praiseworthy but not morally obligatory."
To get around it, you can simply disable that (extremely non-critical) (highly useful) inspection globally, or suppress it for the specific function or statement.
To do so:
PyCharm has its share of small bugs like this, but in my opinion its benefits far outweigh its drawbacks. If you'd like to try another good IDE, there's also Spyder/Spyderlib.
I know this is quite a bit after you asked your question, but I hope this helps (you, or someone else).
Edited: Originally, I thought that this was specific to checking __all__, but it looks like it's the more general 'Unresolved References' check, which can be very useful. It's probably best to use statement-level disabling of the feature, either by using the menu as mentioned above, or by specifying # noinspection PyUnresolvedReferences on the line preceding the statement.