code: void write(CallInfo callInfo, DeltaAssertion assertion) {
      Element rootNode = root(callInfo);
      DataSource ds = assertion.getSource();
      write(rootNode, ds);
      
      Element daNode = createNode(rootNode, DELTA_ASSERTION_TAG);
      List<MetaData.ColumnInfo> mdCols = ds.getMetaData().columns();
      Element expectedNode = createNode(daNode, EXPECTED_TAG);    
      write(expectedNode, 
          OLD_DATA_TAG, 
          mdCols,
          assertion.data(DeltaAssertion.IteratorType.OLD_DATA_EXPECTED));
      write(expectedNode, 
          NEW_DATA_TAG, 
          mdCols,
          assertion.data(DeltaAssertion.IteratorType.NEW_DATA_EXPECTED));
      if (! assertion.passed()) {
        Element errorsNode = createNode(daNode, ERRORS_TAG);
        Element oldDataErrors = createNode(errorsNode, OLD_DATA_TAG);
        Element newDataErrors = createNode(errorsNode, NEW_DATA_TAG);
        write(oldDataErrors, 
            EXPECTED_TAG, 
            mdCols,
            assertion.data(DeltaAssertion.IteratorType.OLD_DATA_ERRORS_EXPECTED));
        write(oldDataErrors, 
            ACTUAL_TAG, 
            mdCols,
            assertion.data(DeltaAssertion.IteratorType.OLD_DATA_ERRORS_ACTUAL));
        write(newDataErrors, 
            EXPECTED_TAG, 
            mdCols,
            assertion.data(DeltaAssertion.IteratorType.NEW_DATA_ERRORS_EXPECTED));
        write(newDataErrors, 
            ACTUAL_TAG, 
            mdCols,
            assertion.data(DeltaAssertion.IteratorType.NEW_DATA_ERRORS_ACTUAL));
      }
      flush(rootNode);
    }
docs: Log delta assertion.
  @param callInfo Call info.
  @param assertion Delta assertion.