Writing Salt modules
There are a few items that are consistent across all Salt modules. These pieces generally work the same way across all module types, though there are a handful of places where you can expect at least a little deviation. We'll cover those in other chapters as we get to them. For now, let's talk about the things that are generally the same.
Hidden objects
It has long been common for programmers to preface functions, variables, and the like with an underscore, if they are only intended to be used internally in the same module. In many languages, objects that are used like this are said to be private objects.
Some environments enforce private behavior by not allowing external code to reference those things directly. Other environments allow it, but its use is discouraged. Salt modules fall into the list of environments that enforce private function behavior; if a function inside a Salt module begins with an underscore, it will not even be exposed to other modules...