code: Iterator<Row> data(IteratorType type) {
      Iterator<Row> itr;
      switch(type) {
        case EXPECTED_DATA:
          itr = data.getRows().iterator();
          break;
        case ERRORS_EXPECTED:
          itr = delta.deleted();
          break;
        case ERRORS_ACTUAL:
          itr = delta.inserted();
          break;
        default:
          throw new InternalErrorException("Unexpected case!");      
      }
      return itr;
    }
docs: Get information for the assertion.
  @param type Type of iterator
  @return An iterator for the specified data.