in src/main/java/jsitter/interop/JSitter.java [18:23]
public static long loadLang(String fnName, String libnameOrPath, ClassLoader loader) {
NativeLibrary instance = NativeLibrary.getInstance(libnameOrPath, loader);
retainedLibs.add(instance);
Function function = instance.getFunction(fnName);
return function.invokeLong(new Object[]{});
}