code: private FlyWeightFlatXmlDataSet buildInternal(InputSource inputSource) throws DataSetException {
          logger.trace("build(inputSource={}) - start", inputSource);
  
          // Validate required parameters
          if (inputSource == null) {
              throw new NullPointerException("The parameter 'inputSource' must not be null");
          }
  
          // Create the flat XML IDataSet
          logger.debug("Creating FlatXmlDataSet with builder parameters: {}", this);
          FlyWeightFlatXmlProducer producer = createProducer(inputSource);
          return new FlyWeightFlatXmlDataSet(producer);
      }
docs: Builds the {@link FlyWeightFlatXmlDataSet} from the parameters that are currently set on this builder
  
  @param inputSource The XML input to be built
  @return The {@link FlyWeightFlatXmlDataSet} built from the configuration of this builder.
  @throws DataSetException