How does any IDE or editor know what some_function would be passed without a severe amount of inspection?
I might be wrong on my definitions, but almost by definition, there's just not enough information before runtime in dynamic systems to infer enough to do any real refactoring or smart completion.
I use PyCharm everyday, and I like it, but it's refactor menu is limited, can fail, and pales in comparison to my uses of java w/ IntelliJ or even a well hinted php app w/ PHPstorm.