docs: public void lengthField(String sourceField, String targetField, String function) {
          TransformationStep step = new TransformationStep();
          step.setSourceFields(sourceField);
          step.setTargetField(targetField);
          step.setOperationParameter(TransformationConstants.LENGTH_FUNCTION_PARAM, function);
          step.setOperationName("length");
          steps.add(step);
      }