Private instance methods and variables should have a [leading underscore](https://github.com/jeremyckahn/lib-tmpl/blob/master/src/library.core.js#L85-L89).

While it is valid to define an instance method in the constructor like this, it should only be done if it is doing something with a variable within the constructor function's closure.  It isn't, in this case.  I'd prefer to keep this distinction clear for this project because it is meant to be educational to others.  Please move this to the `prototype` and outside of the constructor:

````javascript
SubModule.prototype._privateMethod = function (value) {
  this.InstanceVariable = value;
};
````

This way, the method is only defined once, rather than every time the constructor is called.