code: public void forwardField(String sourceField, String targetField) {
          TransformationStep step = new TransformationStep();
          step.setTargetField(targetField);
          step.setSourceFields(sourceField);
          step.setOperationName("forward");
          steps.add(step);
      }
docs: Adds a forward transformation step to the transformation description. The value of the source field is copied to
  the target field unchanged. Both fields need to have the same object type.