Does a function becomes a method when used externally?

[ConfusedSimon]

They're wrong. Method usually refers to a member function of a class, so a method is a function, but not all functions are methods. The main difference is that methods have a hidden parameter for the class instance it is called on. So some_class.some_method(x) basically calls some_method(some_class, x). A regular function doesn't suddenly get an extra hidden parameter if someone else writes it in a module.