code: public void output(String output)
          throws XMLStreamException
      {
          if (mIsFlattening > 0) {
              try {
                  mWriter.write(output);
              } catch (IOException ioe) {
                  throw new WstxIOException(ioe);
              }
          }
      }
docs: Method called when explicit output has to be done for flatten output:
  this is usually done when there's need to do speculative checks
  before it's known if some chars are output (when suppressing comments
  or conditional sections)