public void handleStartElement(
      OtterContentHandler theContentHandler,
      String namespaceURI,
      String localName,
      String qualifiedName,
      Attributes attributes) {
    //
    // should just push the mode - so subsequence tags know we're
    // dealing with a sequence fragment.
    super.handleStartElement(theContentHandler, namespaceURI, localName, qualifiedName, attributes);

    AssemblyFeature sequenceFragment = new AssemblyFeature();
    //
    // pushes annotation on the stack so subsequence tags can
    // modify it.
    theContentHandler.pushStackObject(sequenceFragment);
  } // end handleTag