code: void write(CallInfo callInfo, DataSet data) {
      Element rootNode = root(callInfo);
      write(rootNode, data.getSource());
      Element dsNode = createNode(rootNode, DATA_SET_TAG);
      write(dsNode, ROWS_TAG, data.getSource().getMetaData().columns(), data.getRows().iterator());
      flush(rootNode);
    }
docs: Write a data set to the log.
  @param callInfo Call info.
  @param data Data set.