Can't convert string to lower case in Ruta

I have a functioning RUTA script. All I want to do is convert a string variable to lowercase doing this ASSIGN(s1, toLowerCase(s2)) where both s1 and s2 are strings. My script works when I do this ASSIGN(s1,s2) but causes an error when I add toLowerCase to my script. The error I get is not very helpful.

2021-08-28 11:27:39 ERROR AnnotateFileHandler:67 - org.apache.uima.resource.ResourceInitializationException: Initialization of annotator class "org.apache.uima.ruta.engine.RutaEngine" failed. (Descriptor: )

I found an answer posted by Peter.

here

I had to change the way I was configuring my Ruta engine to import the string functions, like this:

 createEngineDescription(RutaEngine.class,
            RutaEngine.PARAM_MAIN_SCRIPT, "system8.annotator.system8",
            RutaEngine.PARAM_ADDITIONAL_EXTENSIONS,
            new String[]{
                BooleanOperationsExtension.class.getName(),
                StringOperationsExtension.class.getName()})

Thank goodness for Peter Kluegl