code: public <TDPO> TransformedDataProviderContext transform(Transformer<DPO, TDPO> ruleInputTransformer) {
          List<Transformer> addedTransformers = new ArrayList<Transformer>();
          if (ruleInputTransformer != null) {
              addedTransformers.add(ruleInputTransformer);
          }
  
          return new TransformedDataProviderContext<DPO, TDPO>(addedTriggers, addedDataProviders,
                  GeneralValidator.MappingStrategy.SPLIT, addedTransformers);
      }
docs: Adds the specified rule input transformer to the validator under construction.
  
  @param ruleInputTransformer Rule input transformer to be added.
  @param <TDPO>               Type of transformer output.
  
  @return Context allowing further construction of the validator using the DSL.