code.aload().setParam(1);
code.putfield().setField(valueType);
// create change tracker and set it
code.iload().setParam(3);
JumpInstruction ifins = code.ifeq();
code.aload().setLocal(ret);
code.anew().setType(MapChangeTrackerImpl.class);
code.dup();
code.aload().setLocal(ret);
code.invokespecial().setMethod(MapChangeTrackerImpl.class,