code: public <TRO> TransformedRuleContext<DPO, RI, RO, TRO> transform(Transformer<Collection<RO>,
              TRO> resultHandlerInputTransformer) {
          List<Transformer> transformers = new ArrayList<Transformer>();
          if (resultHandlerInputTransformer != null) {
              transformers.add(resultHandlerInputTransformer);
          }
  
          return new TransformedRuleContext<DPO, RI, RO, TRO>(addedTriggers, addedDataProviders,
                  dataProviderToRuleMapping, addedRuleInputTransformers, addedRules,
                  GeneralValidator.MappingStrategy.JOIN, transformers);
      }
docs: Adds the specified result handler input transformer to the validator under construction.
  
  @param resultHandlerInputTransformer Result handler input transformer to be added.
  @param <TRO>                         Type of transformer output.
  
  @return Context allowing further construction of the validator using the DSL.