code: public List<MiningField> getMiningFieldsForModel(String modelId) {
          PMML4Model model = modelsMap.get(modelId);
          if (model != null) {
              return model.getRawMiningFields();
          }
          return null;
      }
docs: Retrieves a List of the raw MiningField objects for a
  given model
  @param modelId The identifier of the model for which the list of MiningField objects is retrieved
  @return The list of MiningField objects belonging to the identified model