Can't pass datasets via iterator to embedded Java

IMPORT Java, Std;
 
kString := RECORD
    INTEGER4 id;
    STRING text;
END;
 
DATASET(kString) init(DATASET(kString) inp, integer4 n) := EMBED(Java: globalscope('keras.ecl'), persist('query'), activity)
import java.util.*;
public class myClass {

  public static class kString {
    String text;
    int id;
    public kString() {}
    public kString(String _text, int _id)
    {
      text = _text;
      id = _id;
    }
  };

  public static Iterator<kString> init(Iterator<kString> in, int n)
  {
    List<kString> list = new ArrayList<>();
    list.add(new kString("init", n));
    return list.iterator();
//    return new kString("init", n);
//    return new kString(in[0].text, in[0].id);
  }
}
ENDEMBED;
 
DATASET(kString) getTest(DATASET(kString) inp, integer4 n) := EMBED(Java: globalscope('keras.ecl'), persist('query'), activity)
import java.util.*;
public class myClass {

  public static class kString {
    String text;
    int id;
    public kString() {}
    public kString(String _text, int _id)
    {
      text = _text;
      id = _id;
    }
  };

  public static Iterator<kString> getTest(kString in[], int n)
  {
    List<kString> list = new ArrayList<>();
    list.add(new kString("getTest", n));
    return list.iterator();
//    return new kString(in[0].text, in[0].id);
  }
}
ENDEMBED;
 
initRslt := init(DATASET([], kString), Std.System.thorlib.node());
o1 := OUTPUT(initRslt, NAMED('initRslt'));
 
getRslt := getTest(DATASET([], kString), Std.System.thorlib.node());
o2 := OUTPUT(getRslt, NAMED('getRslt'));
 
SEQUENTIAL(o1, o2);