private static Collection<String> findFunctionsInThisJar(File jarFile) throws IOException {
    return new FunctionScanner().findFunctionsInJar(jarFile);
  }
Unregisters functions from a previously deployed jar that are not present in its replacement.
If newJar is null, all functions registered from oldJar will be removed.

@param jarFileName - The name of the deployment that linked to the functions that are to be
       unregistered.
geode-core/src/main/java/org/apache/geode/cache/internal/execute/FunctionToFileTracker.java