It may well be it isn't meant to be a "public" function.
While it's conventional to start "internal" functions in a plugin with an underscore _, there's no requirement, and Javascript has no way to hide internal methods.
I note that for example, Validator has a .resetinternals() function. It's almost certain it's not meant for you to call it! MOST plugins would have called this _resetInternals() as a clue that you are not to call it.
You can look at the plugin source (which is a lot easier to read!) at GitHub or download it and search with your favorite editor. I easily found the code for .elements(). I don't think it does what you think.